Antwort How do you explain regular expressions? Weitere Antworten – How do you describe a regular expression

Regular expressions are combinations of special character operators, which are symbols that control the search, that you can use to construct search strings for advanced find and/or replace searches.A regex (regular expression) consists of a sequence of sub-expressions. In this example, [0-9] and + . The […] , known as character class (or bracket list), encloses a list of characters. It matches any SINGLE character in the list.Basic concepts. A regular expression, often called a pattern, specifies a set of strings required for a particular purpose. A simple way to specify a finite set of strings is to list its elements or members.

What do you need to know about regular expressions : Regular Expression is a pattern describing a certain amount of text. This pattern is used in most of the programming languages to identify text in strings. Usually such patterns are used by string-searching algorithms for "find" or "find and replace" operations on strings, or for input validation.

What does *$ mean in regex

.wDYxhc{clear:both}.cUnQKe .wDYxhc,.related-question-pair .wDYxhc,.M8OgIe .fm06If .wDYxhc{clear:none}html .dG2XIf .xpdclose .LKPcQc,html .dG2XIf .xpdopen .viOShc{padding-top:0;}.garHBe{color:var(–COEmY);font-size:20px;line-height:1.3;position:relative}.garHBe a{color:var(–COEmY)}.xpdopen .Hhmu2e{overflow:inherit}.xpdclose .a84NUc:not(:empty),.xpdopen .CQKTwc:not(:empty){border-top:solid 1px #ebebeb;border-radius:0}.xpdclose .pmYXee .a84NUc:not(:empty),.xpdopen .pmYXee .CQKTwc:not(:empty){border-top:none}.cAn2Qb .a84NUc:not(:empty),.cAn2Qb .CQKTwc:not(:empty){border-top:none}.SHa8ve{display:none}.xpdclose .TOfaBb.SHa8ve,.xpdopen .LL5J7d.SHa8ve{display:block}.rKR6H{padding-top:0.1px}.xpdclose .oHglmf,.xpdopen .xzPb7d{padding-bottom:16px}.xpdclose .kp-header .oHglmf,.xpdopen .kp-header .xzPb7d{padding-bottom:0}.c2xzTb .xpdclose .oHglmf,.c2xzTb .xpdopen .xzPb7d{padding-bottom:0}.HSryR .xpdclose .oHglmf,.HSryR .xpdopen .xzPb7d{padding-bottom:0}.Wnoohf .xpdopen .yp1CPe,.OJXvsb .xpdclose .siXlze{padding-bottom:16px}.Wnoohf .xpdopen .yp1CPe .xpdbox g-more-link{top:28px}.Wnoohf .xpdclose .wDYxhc.xsZWvb,.Wnoohf .xpdopen .wDYxhc.EfDVh{padding-bottom:0}.OJXvsb .xpdclose .wDYxhc.siXlze{padding-bottom:16px}#rhs .dG2XIf .xpdclose .LKPcQc,#rhs .dG2XIf .xpdopen .viOShc{padding-top:0}#rhs .Wnoohf .xpdopen .yp1CPe,#rhs .OJXvsb .xpdclose .siXlze{padding-bottom:15px}#rhs .Wnoohf .xpdclose .wDYxhc.xsZWvb,#rhs .Wnoohf .xpdopen .wDYxhc.EfDVh{padding-bottom:0}#rhs .Wnoohf .xpdclose .wDYxhc.xsZWvb.ecRggb,#rhs .Wnoohf .xpdopen .wDYxhc.EfDVh.ecRggb,#rhs .dG2XIf .ecRggb{padding-bottom:15px}.ecRggb{background-color:#fff;box-shadow:none;border:1px solid #dadce0;border-radius:8px;margin:0 0 16px 0}.tWSgNb .cAn2Qb{border-bottom:none}.IiOSLb .rsGxI.Ww4FFb,.Ww4FFb{background-color:var(–xhUGwc);border-radius:0px;border-width:0;box-shadow:none}.Ww4FFb .mnr-c:not(:empty),.mnr-c:not(:empty) .Ww4FFb,.Ww4FFb .Ww4FFb{box-shadow:none;margin-bottom:0px}.vt6azd{margin:0px 0px 8px}.vt6azd{margin:0px 0px 30px}.CBvvz{margin:-var(–sds-sys-measurement–space-sm) 0px 0px}.CBvvz{margin:-30px 0px 0px}.Jb0Zif .UiGGAb.ILfuVd,.ILfuVd{font-size:16px;line-height:24px;}.fm06If .ILfuVd.NA6bn,.c2xzTb .ILfuVd.duSGDe,.c2xzTb .ILfuVd.NA6bn.c3biWd{font-size:14px;line-height:1.58;}.c2xzTb .zloOqf{font-size:16px;margin-bottom:16px;margin-top:-8px;}.FLWspc{margin:16px}.LFYdN{font-size:16px;margin:16px}.trNcde .ILfuVd{color:var(–bbQxAb);font-family:Google Sans,arial,sans-serif;font-size:14px;line-height:22px}.HSryR .ILfuVd{line-height:1.5}.ss6qqb .ILfuVd,.ss6qqb .UiGGAb.ILfuVd{font-size:14px;line-height:22px}.c2xzTb .qLYAZd{margin:16px 16px 16px 0;}.d9FyLd{padding:0 0 10px}.hgKElc{padding:0 8px 0 0}.kX21rb{font-size:12px;line-height:1.34;display:inline-block;font-family:Google Sans,arial,sans-serif;padding-right:0;white-space:nowrap}.SPV4pd{display:flex;overflow-x:auto}.SPV4pd::-webkit-scrollbar{display:none}.Vjskue{margin-left:8px}.JT9o0,.ZnIJV{align-items:center;border:1px solid var(–mXZkqc);border-radius:16px;box-sizing:border-box;color:#1a73e8;cursor:pointer;display:flex;height:32px;margin-bottom:16px}.BkHX0d{font-family:Google Sans,arial,sans-serif-medium,sans-serif;font-size:14px;line-height:20px;padding-right:20px;text-align:center;white-space:nowrap}.xv1D5b{display:block;padding:0 8px 0 12px;width:18px;height:18px}.LGOjhe{overflow:hidden;padding-bottom:20px}.trNcde .LGOjhe{overflow:visible}.SALvLe .LGOjhe,.Jb0Zif .LGOjhe,.HSryR .LGOjhe,.IVvPP .LGOjhe{padding:0 0 10px;margin:10px 0 0 0}.s6JM6d .SALvLe .LGOjhe{margin-top:12px;}.s6JM6d .HSryR .LGOjhe{margin-top:12px;padding-bottom:20px}#res .Jb0Zif .qDOt0b h3,.IVvPP .qDOt0b h3{font-size:16px;line-height:1.375}.Jb0Zif .qDOt0b .iUh30,.IVvPP .qDOt0b .iUh30{font-size:14px;line-height:1.58}.IVvPP .qDOt0b{border-bottom:1px solid var(–gS5jXb);padding-bottom:6px}.rjOVwe.ILfuVd{font-size:16px;line-height:20px}.dG2XIf .rjOVwe{padding-top:22px;padding-bottom:0;margin-bottom:1px}.xWd7I{padding-top:12px;}.ILfuVd.NA6bn,.ILfuVd.duSGDe,.ILfuVd.UiGGAb,.IVvPP .ILfuVd{font-size:14px;line-height:22px}.n6SJS .ILfuVd{font-size:14px}.ILfuVd.NA6bn,.ILfuVd.duSGDe,.ILfuVd.UiGGAb,.IVvPP .ILfuVd{line-height:20px}.xpd-wa .g-blk{margin:initial}.xpd-wa .dG2XIf{border:initial;box-shadow:none}.fm06If .ILfuVd,.c2xzTb .ILfuVd,.Jb0Zif .c2xzTb .ILfuVd{font-family:Google Sans,arial,sans-serif;color:var(–YLNNHc)}.fm06If .ILfuVd,.c2xzTb .ILfuVd,.Jb0Zif .c2xzTb .ILfuVd{font-size:20px;line-height:28px}.cUnQKe .ILfuVd,.cUnQKe .UiGGAb.ILfuVd,.w5mTAe .ILfuVd,.W0urI .ILfuVd{color:var(–bbQxAb);font-family:Google Sans,arial,sans-serif;font-size:16px;line-height:24px}.fm06If .ILfuVd b,.trNcde .ILfuVd b,.cUnQKe .ILfuVd b,.c2xzTb .ILfuVd b,.w5mTAe .ILfuVd b,.W0urI .ILfuVd b{background-color:#d3e3fd;color:#040c28;font-weight:500}@media (forced-colors:active){.fm06If .ILfuVd b,.c2xzTb .ILfuVd b,.trNcde .ILfuVd b,.cUnQKe .ILfuVd b,.w5mTAe .ILfuVd b,.W0urI .ILfuVd b{background-color:Mark;color:MarkText}}.vBnbff .mO5MMe{padding-top:10px}.cUnQKe .vBnbff .mO5MMe{padding-left:0;}.trNcde .vBnbff .mO5MMe{padding:10px 0 0 0}.cAn2Qb.abzPbc .mnr-c{max-width:calc(100% – 162px)}.tF2Cxc{position:relative}.Jb0Zif .BDNLRc{margin:16px 16px -11px}.RUXr2d{display:inline}.MTB56{margin-right:12px;vertical-align:middle}.Pthbuf{display:flex;align-items:center}.m164Nd{vertical-align:middle;display:inline-block}.qpGQpf{clear:both;padding-top:6px}.aCOpRe{line-height:1.58;word-wrap:break-word}.aCOpRe sup{line-height:0.9}.yuRUbf{font-weight:normal;font-size:small;line-height:1.58;}.IsZvec{max-width:48em;color:#4d5156;line-height:1.58}.uo4vr{color:var(–IXoxUe);line-height:1.58}.IjZ7ze{display:inline-block;color:var(–IXoxUe);font-size:12px;line-height:1.34;white-space:nowrap}.FyYA1e{margin:5px 0}a:hover h3.LC20lb{text-decoration:underline}.M8OgIe .dG2XIf .fm06If .LC20lb,.n6SJS h3.LC20lb{overflow:hidden;text-overflow:ellipsis;white-space:nowrap;width:100%}.LC20lb{display:inline-block;line-height:1.3;margin-bottom:3px;}.c2xzTb .LC20lb{margin-bottom:0}.MMgsKf{padding-top:2px}.DKV0Md{padding-top:4px;padding-top:5px;}.Z3xoIb{padding-top:27px;padding-top:28px;}.NXKJM{display:-webkit-box;overflow:hidden;-webkit-box-orient:vertical;-webkit-line-clamp:1}.hceuRc{-webkit-box-orient:vertical;display:-webkit-box;-webkit-line-clamp:2;overflow:hidden}.fzBvHb{font-weight:700}.DKV0Md,.Z3xoIb{margin-top:18px;}.xvfwl{margin-top:4px}.q0vns a.fl{font-size:12px}.TQc1id .qLRx3b{font-size:14px;line-height:1.58}.HGLrXd{display:inline-block;-webkit-text-size-adjust:none}.q0vns{display:inline-block;padding-bottom:2px;padding-top:1px}.NJjxre{position:absolute;left:0;top:0;width:100%}.M8OgIe .VWCdhc.Mjve0e .q0vns{width:max-content}.VjDLd .TieM1d .tjvcx,.IVvPP .tjvcx,.kno-kp .tjvcx,.VjDLd .kp-wholepage-osrp .tjvcx,#rhs .ss6qqb .tjvcx,#rhs .trNcde .tjvcx{display:inline-block;height:19px;overflow-y:hidden}.ojE3Fb{padding:0;padding-bottom:0;}.ojE3Fb .q0vns{display:flex;overflow:hidden;padding:0;padding-bottom:0;align-items:center;}.ojE3Fb .q0vns a.fl{padding-top:0;font-size:12px;line-height:18px;}.GvPZzd{font-size:12px;line-height:18px;}.dTxz9{padding-right:38px}.iG7WGe{color:#202124;padding:0;text-align:center;width:16px}.VuuXrf{color:#202124;font-size:14px;display:block;line-height:20px;white-space:nowrap;}.qncq2c{font-size:12px;line-height:16px;margin-left:6px}.CA5RN{overflow:hidden}.K2VDSb{display:flex;flex-direction:row}.H9lube{background-color:#f1f3f4;border:1px solid #dadce0;border-radius:50%;display:inline-flex;justify-content:center;align-items:center;height:26px;width:26px;margin-right:12px;flex-shrink:0;vertical-align:middle;}.fJOpI.H9lube{background-color:#e2eeff;border:1px solid #e2eeff}.P1UpZb{background-color:#f1f3f4;border:1px solid #ecedef}.eqA2re.NjwKYd{margin-right:0}.Vwoesf:not(.oRVWZ){display:inline-block}.Vwoesf{vertical-ali
gn:middle}.XNo5Ab.XNo5Ab{display:block;}.lWlVCe{border-radius:50%}.bJVp8c{color:#0060f0}.Jj3Uob{color:#0060f0;}.ob9lvb{color:#4d5156}.ob9lvb.HCMUuf{color:var(–IXoxUe)}.ylgVCe{color:#4d5156}.B6fmyf{position:absolute;top:0;height:0;visibility:hidden;white-space:nowrap;width:100%}.B6fmyf.Mg1HEd{height:auto}.ljeAnf{display:-webkit-box;overflow:hidden;-webkit-box-orient:vertical}.byrV5b{align-items:center;display:flex;flex-direction:row}.sBJG1d{display:flex;flex-direction:row;justify-content:center}.kDmHO{align-items:center;display:flex;flex-direction:column}.lR4vec{display:flex;flex-direction:column;justify-content:center}.xTEyc{align-items:start;display:flex;flex-direction:row}.OjFzvd{display:flex;flex-direction:row;justify-content:start}.YIPhrb{align-items:start;display:flex;flex-direction:column}.BToiNc{display:flex;flex-direction:column;justify-content:start}.E4bmEc .Va021{flex:1 1 100%}.E4bmEc .Y76LGf{flex:1 1 calc(50% – 4px)}
*$ means – match, from beginning to end, any character that appears zero or more times. Basically, that means – match everything from start to end of the string. This regex pattern is not very useful.

What does a regular expression represent : .wDYxhc{clear:both}.cUnQKe .wDYxhc,.related-question-pair .wDYxhc,.M8OgIe .fm06If .wDYxhc{clear:none}html .dG2XIf .xpdclose .LKPcQc,html .dG2XIf .xpdopen .viOShc{padding-top:0;}.garHBe{color:var(–COEmY);font-size:20px;line-height:1.3;position:relative}.garHBe a{color:var(–COEmY)}.xpdopen .Hhmu2e{overflow:inherit}.xpdclose .a84NUc:not(:empty),.xpdopen .CQKTwc:not(:empty){border-top:solid 1px #ebebeb;border-radius:0}.xpdclose .pmYXee .a84NUc:not(:empty),.xpdopen .pmYXee .CQKTwc:not(:empty){border-top:none}.cAn2Qb .a84NUc:not(:empty),.cAn2Qb .CQKTwc:not(:empty){border-top:none}.SHa8ve{display:none}.xpdclose .TOfaBb.SHa8ve,.xpdopen .LL5J7d.SHa8ve{display:block}.rKR6H{padding-top:0.1px}.xpdclose .oHglmf,.xpdopen .xzPb7d{padding-bottom:16px}.xpdclose .kp-header .oHglmf,.xpdopen .kp-header .xzPb7d{padding-bottom:0}.c2xzTb .xpdclose .oHglmf,.c2xzTb .xpdopen .xzPb7d{padding-bottom:0}.HSryR .xpdclose .oHglmf,.HSryR .xpdopen .xzPb7d{padding-bottom:0}.Wnoohf .xpdopen .yp1CPe,.OJXvsb .xpdclose .siXlze{padding-bottom:16px}.Wnoohf .xpdopen .yp1CPe .xpdbox g-more-link{top:28px}.Wnoohf .xpdclose .wDYxhc.xsZWvb,.Wnoohf .xpdopen .wDYxhc.EfDVh{padding-bottom:0}.OJXvsb .xpdclose .wDYxhc.siXlze{padding-bottom:16px}#rhs .dG2XIf .xpdclose .LKPcQc,#rhs .dG2XIf .xpdopen .viOShc{padding-top:0}#rhs .Wnoohf .xpdopen .yp1CPe,#rhs .OJXvsb .xpdclose .siXlze{padding-bottom:15px}#rhs .Wnoohf .xpdclose .wDYxhc.xsZWvb,#rhs .Wnoohf .xpdopen .wDYxhc.EfDVh{padding-bottom:0}#rhs .Wnoohf .xpdclose .wDYxhc.xsZWvb.ecRggb,#rhs .Wnoohf .xpdopen .wDYxhc.EfDVh.ecRggb,#rhs .dG2XIf .ecRggb{padding-bottom:15px}.ecRggb{background-color:#fff;box-shadow:none;border:1px solid #dadce0;border-radius:8px;margin:0 0 16px 0}.tWSgNb .cAn2Qb{border-bottom:none}.Jb0Zif .UiGGAb.ILfuVd,.ILfuVd{font-size:16px;line-height:24px;}.fm06If .ILfuVd.NA6bn,.c2xzTb .ILfuVd.duSGDe,.c2xzTb .ILfuVd.NA6bn.c3biWd{font-size:14px;line-height:1.58;}.c2xzTb .zloOqf{font-size:16px;margin-bottom:16px;margin-top:-8px;}.FLWspc{margin:16px}.LFYdN{font-size:16px;margin:16px}.trNcde .ILfuVd{color:var(–bbQxAb);font-family:Google Sans,arial,sans-serif;font-size:14px;line-height:22px}.HSryR .ILfuVd{line-height:1.5}.ss6qqb .ILfuVd,.ss6qqb .UiGGAb.ILfuVd{font-size:14px;line-height:22px}.c2xzTb .qLYAZd{margin:16px 16px 16px 0;}.d9FyLd{padding:0 0 10px}.hgKElc{padding:0 8px 0 0}.kX21rb{font-size:12px;line-height:1.34;display:inline-block;font-family:Google Sans,arial,sans-serif;padding-right:0;white-space:nowrap}.SPV4pd{display:flex;overflow-x:auto}.SPV4pd::-webkit-scrollbar{display:none}.Vjskue{margin-left:8px}.JT9o0,.ZnIJV{align-items:center;border:1px solid var(–mXZkqc);border-radius:16px;box-sizing:border-box;color:#1a73e8;cursor:pointer;display:flex;height:32px;margin-bottom:16px}.BkHX0d{font-family:Google Sans,arial,sans-serif-medium,sans-serif;font-size:14px;line-height:20px;padding-right:20px;text-align:center;white-space:nowrap}.xv1D5b{display:block;padding:0 8px 0 12px;width:18px;height:18px}.LGOjhe{overflow:hidden;padding-bottom:20px}.trNcde .LGOjhe{overflow:visible}.SALvLe .LGOjhe,.Jb0Zif .LGOjhe,.HSryR .LGOjhe,.IVvPP .LGOjhe{padding:0 0 10px;margin:10px 0 0 0}.s6JM6d .SALvLe .LGOjhe{margin-top:12px;}.s6JM6d .HSryR .LGOjhe{margin-top:12px;padding-bottom:20px}#res .Jb0Zif .qDOt0b h3,.IVvPP .qDOt0b h3{font-size:16px;line-height:1.375}.Jb0Zif .qDOt0b .iUh30,.IVvPP .qDOt0b .iUh30{font-size:14px;line-height:1.58}.IVvPP .qDOt0b{border-bottom:1px solid var(–gS5jXb);padding-bottom:6px}.rjOVwe.ILfuVd{font-size:16px;line-height:20px}.dG2XIf .rjOVwe{padding-top:22px;padding-bottom:0;margin-bottom:1px}.xWd7I{padding-top:12px;}.ILfuVd.NA6bn,.ILfuVd.duSGDe,.ILfuVd.UiGGAb,.IVvPP .ILfuVd{font-size:14px;line-height:22px}.n6SJS .ILfuVd{font-size:14px}.ILfuVd.NA6bn,.ILfuVd.duSGDe,.ILfuVd.UiGGAb,.IVvPP .ILfuVd{line-height:20px}.xpd-wa .g-blk{margin:initial}.xpd-wa .dG2XIf{border:initial;box-shadow:none}.fm06If .ILfuVd,.c2xzTb .ILfuVd,.Jb0Zif .c2xzTb .ILfuVd{font-family:Google Sans,arial,sans-serif;color:var(–YLNNHc)}.fm06If .ILfuVd,.c2xzTb .ILfuVd,.Jb0Zif .c2xzTb .ILfuVd{font-size:20px;line-height:28px}.cUnQKe .ILfuVd,.cUnQKe .UiGGAb.ILfuVd,.w5mTAe .ILfuVd,.W0urI .ILfuVd{color:var(–bbQxAb);font-family:Google Sans,arial,sans-serif;font-size:16px;line-height:24px}.fm06If .ILfuVd b,.trNcde .ILfuVd b,.cUnQKe .ILfuVd b,.c2xzTb .ILfuVd b,.w5mTAe .ILfuVd b,.W0urI .ILfuVd b{background-color:#d3e3fd;color:#040c28;font-weight:500}@media (forced-colors:active){.fm06If .ILfuVd b,.c2xzTb .ILfuVd b,.trNcde .ILfuVd b,.cUnQKe .ILfuVd b,.w5mTAe .ILfuVd b,.W0urI .ILfuVd b{background-color:Mark;color:MarkText}}.vBnbff .mO5MMe{padding-top:10px}.cUnQKe .vBnbff .mO5MMe{padding-left:0;}.trNcde .vBnbff .mO5MMe{padding:10px 0 0 0}.cAn2Qb.abzPbc .mnr-c{max-width:calc(100% – 162px)}.tF2Cxc{position:relative}.Jb0Zif .BDNLRc{margin:16px 16px -11px}.RUXr2d{display:inline}.MTB56{margin-right:12px;vertical-align:middle}.Pthbuf{display:flex;align-items:center}.m164Nd{vertical-align:middle;display:inline-block}.qpGQpf{clear:both;padding-top:6px}.aCOpRe{line-height:1.58;word-wrap:break-word}.aCOpRe sup{line-height:0.9}.yuRUbf{font-weight:normal;font-size:small;line-height:1.58;}.IsZvec{max-width:48em;color:#4d5156;line-height:1.58}.uo4vr{color:var(–IXoxUe);line-height:1.58}.IjZ7ze{display:inline-block;color:var(–IXoxUe);font-size:12px;line-height:1.34;white-space:nowrap}.FyYA1e{margin:5px 0}a:hover h3.LC20lb{text-decoration:underline}.M8OgIe .dG2XIf .fm06If .LC20lb,.n6SJS h3.LC20lb{overflow:hidden;text-overflow:ellipsis;white-space:nowrap;width:100%}.LC20lb{display:inline-block;line-height:1.3;margin-bottom:3px;}.c2xzTb .LC20lb{margin-bottom:0}.MMgsKf{padding-top:2px}.DKV0Md{padding-top:4px;padding-top:5px;}.Z3xoIb{padding-top:27px;padding-top:28px;}.NXKJM{display:-webkit-box;overflow:hidden;-webkit-box-orient:vertical;-webkit-line-clamp:1}.hceuRc{-webkit-box-orient:vertical;display:-webkit-box;-webkit-line-clamp:2;overflow:hidden}.fzBvHb{font-weight:700}.DKV0Md,.Z3xoIb{margin-top:18px;}.xvfwl{margin-top:4px}.q0vns a.fl{font-size:12px}.TQc1id .qLRx3b{font-size:14px;line-height:1.58}.HGLrXd{display:inline-block;-webkit-text-size-adjust:none}.q0vns{display:inline-block;padding-bottom:2px;padding-top:1px}.NJjxre{position:absolute;left:0;top:0;width:100%}.M8OgIe .VWCdhc.Mjve0e .q0vns{width:max-content}.VjDLd .TieM1d .tjvcx,.IVvPP .tjvcx,.kno-kp .tjvcx,.VjDLd .kp-wholepage-osrp .tjvcx,#rhs .ss6qqb .tjvcx,#rhs .trNcde .tjvcx{display:inline-block;height:19px;overflow-y:hidden}.ojE3Fb{padding:0;padding-bottom:0;}.ojE3Fb .q0vns{display:flex;overflow:hidden;padding:0;padding-bottom:0;align-items:center;}.ojE3Fb .q0vns a.fl{padding-top:0;font-size:12px;line-height:18px;}.GvPZzd{font-size:12px;line-height:18px;}.dTxz9{padding-right:38px}.iG7WGe{color:#202124;padding:0;text-align:center;width:16px}.VuuXrf{color:#202124;font-size:14px;display:block;line-height:20px;white-space:nowrap;}.qncq2c{font-size:12px;line-height:16px;margin-left:6px}.CA5RN{overflow:hidden}.K2VDSb{display:flex;flex-direction:row}.H9lube{background-color:#f1f3f4;border:1px solid #dadce0;border-radius:50%;display:inline-flex;justify-content:center;align-items:center;height:26px;width:26px;margin-right:12px;flex-shrink:0;vertical-align:middle;}.fJOpI.H9lube{background-color:#e2eeff;border:1px solid #e2eeff}.P1UpZb{background-color:#f1f3f4;border:1px solid #ecedef}.eqA2re.NjwKYd{margin-right:0}.Vwoesf:not(.oRVWZ){display:inline-block}.Vwoesf{vertical-align:middle}.XNo5Ab.XNo5Ab{display:block;}.lWlVCe{border-radius:50%}.bJVp8c{color:#0060f0}.Jj3Uob{color:#0060f0;}.ob9lvb{color:#4d5156}.ob9lvb.HCMUuf{color:var(–IXoxUe)}.ylgVCe{color:#4d5156}.B6fmyf{position:absolute;top:0;height:0;visibility:hidden;white-space:nowrap;width:100%}.B6fmyf.Mg1HEd{height:auto}.ljeAnf{display:-webkit-box;overflow:hidden;-webkit-box-orient:vertical}
A regular expression is a pattern that can match repeating characters or strings, and alternative characters or strings. The repetition and alternation are expressed using metacharacters such as *, +, and | in patterns.

.wDYxhc{clear:both}.cUnQKe .wDYxhc,.related-question-pair .wDYxhc,.M8OgIe .fm06If .wDYxhc{clear:none}html .dG2XIf .xpdclose .LKPcQc,html .dG2XIf .xpdopen .viOShc{padding-top:0;}.garHBe{color:var(–COEmY);font-size:20px;line-height:1.3;position:relative}.garHBe a{color:var(–COEmY)}.xpdopen .Hhmu2e{overflow:inherit}.xpdclose .a84NUc:not(:empty),.xpdopen .CQKTwc:not(:empty){border-top:solid 1px #ebebeb;border-radius:0}.xpdclose .pmYXee .a84NUc:not(:empty),.xpdopen .pmYXee .CQKTwc:not(:empty){border-top:none}.cAn2Qb .a84NUc:not(:empty),.cAn2Qb .CQKTwc:not(:empty){border-top:none}.SHa8ve{display:none}.xpdclose .TOfaBb.SHa8ve,.xpdopen .LL5J7d.SHa8ve{display:block}.rKR6H{padding-top:0.1px}.xpdclose .oHglmf,.xpdopen .xzPb7d{padding-bottom:16px}.xpdclose .kp-header .oHglmf,.xpdopen .kp-header .xzPb7d{padding-bottom:0}.c2xzTb .xpdclose .oHglmf,.c2xzTb .xpdopen .xzPb7d{padding-bottom:0}.HSryR .xpdclose .oHglmf,.HSryR .xpdopen .xzPb7d{padding-bottom:0}.Wnoohf .xpdopen .yp1CPe,.OJXvsb .xpdclose .siXlze{padding-bottom:16px}.Wnoohf .xpdopen .yp1CPe .xpdbox g-more-link{top:28px}.Wnoohf .xpdclose .wDYxhc.xsZWvb,.Wnoohf .xpdopen .wDYxhc.EfDVh{padding-bottom:0}.OJXvsb .xpdclose .wDYxhc.siXlze{padding-bottom:16px}#rhs .dG2XIf .xpdclose .LKPcQc,#rhs .dG2XIf .xpdopen .viOShc{padding-top:0}#rhs .Wnoohf .xpdopen .yp1CPe,#rhs .OJXvsb .xpdclose .siXlze{padding-bottom:15px}#rhs .Wnoohf .xpdclose .wDYxhc.xsZWvb,#rhs .Wnoohf .xpdopen .wDYxhc.EfDVh{padding-bottom:0}#rhs .Wnoohf .xpdclose .wDYxhc.xsZWvb.ecRggb,#rhs .Wnoohf .xpdopen .wDYxhc.EfDVh.ecRggb,#rhs .dG2XIf .ecRggb{padding-bottom:15px}.ecRggb{background-color:#fff;box-shadow:none;border:1px solid #dadce0;border-radius:8px;margin:0 0 16px 0}.tWSgNb .cAn2Qb{border-bottom:none}.Jb0Zif .UiGGAb.ILfuVd,.ILfuVd{font-size:16px;line-height:24px;}.fm06If .ILfuVd.NA6bn,.c2xzTb .ILfuVd.duSGDe,.c2xzTb .ILfuVd.NA6bn.c3biWd{font-size:14px;line-height:1.58;}.c2xzTb .zloOqf{font-size:16px;margin-bottom:16px;margin-top:-8px;}.FLWspc{margin:16px}.LFYdN{font-size:16px;margin:16px}.trNcde .ILfuVd{color:var(–bbQxAb);font-family:Google Sans,arial,sans-serif;font-size:14px;line-height:22px}.HSryR .ILfuVd{line-height:1.5}.ss6qqb .ILfuVd,.ss6qqb .UiGGAb.ILfuVd{font-size:14px;line-height:22px}.c2xzTb .qLYAZd{margin:16px 16px 16px 0;}.d9FyLd{padding:0 0 10px}.hgKElc{padding:0 8px 0 0}.kX21rb{font-size:12px;line-height:1.34;display:inline-block;font-family:Google Sans,arial,sans-serif;padding-right:0;white-space:nowrap}.SPV4pd{display:flex;overflow-x:auto}.SPV4pd::-webkit-scrollbar{display:none}.Vjskue{margin-left:8px}.JT9o0,.ZnIJV{align-items:center;border:1px solid var(–mXZkqc);border-radius:16px;box-sizing:border-box;color:#1a73e8;cursor:pointer;display:flex;height:32px;margin-bottom:16px}.BkHX0d{font-family:Google Sans,arial,sans-serif-medium,sans-serif;font-size:14px;line-height:20px;padding-right:20px;text-align:center;white-space:nowrap}.xv1D5b{display:block;padding:0 8px 0 12px;width:18px;height:18px}.LGOjhe{overflow:hidden;padding-bottom:20px}.trNcde .LGOjhe{overflow:visible}.SALvLe .LGOjhe,.Jb0Zif .LGOjhe,.HSryR .LGOjhe,.IVvPP .LGOjhe{padding:0 0 10px;margin:10px 0 0 0}.s6JM6d .SALvLe .LGOjhe{margin-top:12px;}.s6JM6d .HSryR .LGOjhe{margin-top:12px;padding-bottom:20px}#res .Jb0Zif .qDOt0b h3,.IVvPP .qDOt0b h3{font-size:16px;line-height:1.375}.Jb0Zif .qDOt0b .iUh30,.IVvPP .qDOt0b .iUh30{font-size:14px;line-height:1.58}.IVvPP .qDOt0b{border-bottom:1px solid var(–gS5jXb);padding-bottom:6px}.rjOVwe.ILfuVd{font-size:16px;line-height:20px}.dG2XIf .rjOVwe{padding-top:22px;padding-bottom:0;margin-bottom:1px}.xWd7I{padding-top:12px;}.ILfuVd.NA6bn,.ILfuVd.duSGDe,.ILfuVd.UiGGAb,.IVvPP .ILfuVd{font-size:14px;line-height:22px}.n6SJS .ILfuVd{font-size:14px}.ILfuVd.NA6bn,.ILfuVd.duSGDe,.ILfuVd.UiGGAb,.IVvPP .ILfuVd{line-height:20px}.xpd-wa .g-blk{margin:initial}.xpd-wa .dG2XIf{border:initial;box-shadow:none}.fm06If .ILfuVd,.c2xzTb .ILfuVd,.Jb0Zif .c2xzTb .ILfuVd{font-family:Google Sans,arial,sans-serif;color:var(–YLNNHc)}.fm06If .ILfuVd,.c2xzTb .ILfuVd,.Jb0Zif .c2xzTb .ILfuVd{font-size:20px;line-height:28px}.cUnQKe .ILfuVd,.cUnQKe .UiGGAb.ILfuVd,.w5mTAe .ILfuVd,.W0urI .ILfuVd{color:var(–bbQxAb);font-family:Google Sans,arial,sans-serif;font-size:16px;line-height:24px}.fm06If .ILfuVd b,.trNcde .ILfuVd b,.cUnQKe .ILfuVd b,.c2xzTb .ILfuVd b,.w5mTAe .ILfuVd b,.W0urI .ILfuVd b{background-color:#d3e3fd;color:#040c28;font-weight:500}@media (forced-colors:active){.fm06If .ILfuVd b,.c2xzTb .ILfuVd b,.trNcde .ILfuVd b,.cUnQKe .ILfuVd b,.w5mTAe .ILfuVd b,.W0urI .ILfuVd b{background-color:Mark;color:MarkText}}.vBnbff .mO5MMe{padding-top:10px}.cUnQKe .vBnbff .mO5MMe{padding-left:0;}.trNcde .vBnbff .mO5MMe{padding:10px 0 0 0}.cAn2Qb.abzPbc .mnr-c{max-width:calc(100% – 162px)}.tF2Cxc{position:relative}.Jb0Zif .BDNLRc{margin:16px 16px -11px}.RUXr2d{display:inline}.MTB56{margin-right:12px;vertical-align:middle}.Pthbuf{display:flex;align-items:center}.m164Nd{vertical-align:middle;display:inline-block}.qpGQpf{clear:both;padding-top:6px}.aCOpRe{line-height:1.58;word-wrap:break-word}.aCOpRe sup{line-height:0.9}.yuRUbf{font-weight:normal;font-size:small;line-height:1.58;}.IsZvec{max-width:48em;color:#4d5156;line-height:1.58}.uo4vr{color:var(–IXoxUe);line-height:1.58}.IjZ7ze{display:inline-block;color:var(–IXoxUe);font-size:12px;line-height:1.34;white-space:nowrap}.FyYA1e{margin:5px 0}a:hover h3.LC20lb{text-decoration:underline}.M8OgIe .dG2XIf .fm06If .LC20lb,.n6SJS h3.LC20lb{overflow:hidden;text-overflow:ellipsis;white-space:nowrap;width:100%}.LC20lb{display:inline-block;line-height:1.3;margin-bottom:3px;}.c2xzTb .LC20lb{margin-bottom:0}.MMgsKf{padding-top:2px}.DKV0Md{padding-top:4px;padding-top:5px;}.Z3xoIb{padding-top:27px;padding-top:28px;}.NXKJM{display:-webkit-box;overflow:hidden;-webkit-box-orient:vertical;-webkit-line-clamp:1}.hceuRc{-webkit-box-orient:vertical;display:-webkit-box;-webkit-line-clamp:2;overflow:hidden}.fzBvHb{font-weight:700}.DKV0Md,.Z3xoIb{margin-top:18px;}.xvfwl{margin-top:4px}.q0vns a.fl{font-size:12px}.TQc1id .qLRx3b{font-size:14px;line-height:1.58}.HGLrXd{display:inline-block;-webkit-text-size-adjust:none}.q0vns{display:inline-block;padding-bottom:2px;padding-top:1px}.NJjxre{position:absolute;left:0;top:0;width:100%}.M8OgIe .VWCdhc.Mjve0e .q0vns{width:max-content}.VjDLd .TieM1d .tjvcx,.IVvPP .tjvcx,.kno-kp .tjvcx,.VjDLd .kp-wholepage-osrp .tjvcx,#rhs .ss6qqb .tjvcx,#rhs .trNcde .tjvcx{display:inline-block;height:19px;overflow-y:hidden}.ojE3Fb{padding:0;padding-bottom:0;}.ojE3Fb .q0vns{display:flex;overflow:hidden;padding:0;padding-bottom:0;align-items:center;}.ojE3Fb .q0vns a.fl{padding-top:0;font-size:12px;line-height:18px;}.GvPZzd{font-size:12px;line-height:18px;}.dTxz9{padding-right:38px}.iG7WGe{color:#202124;padding:0;text-align:center;width:16px}.VuuXrf{color:#202124;font-size:14px;display:block;line-height:20px;white-space:nowrap;}.qncq2c{font-size:12px;line-height:16px;margin-left:6px}.CA5RN{overflow:hidden}.K2VDSb{display:flex;flex-direction:row}.H9lube{background-color:#f1f3f4;border:1px solid #dadce0;border-radius:50%;display:inline-flex;justify-content:center;align-items:center;height:26px;width:26px;margin-right:12px;flex-shrink:0;vertical-align:middle;}.fJOpI.H9lube{background-color:#e2eeff;border:1px solid #e2eeff}.P1UpZb{background-color:#f1f3f4;border:1px solid #ecedef}.eqA2re.NjwKYd{margin-right:0}.Vwoesf:not(.oRVWZ){display:inline-block}.Vwoesf{vertical-align:middle}.XNo5Ab.XNo5Ab{display:block;}.lWlVCe{border-radius:50%}.bJVp8c{color:#0060f0}.Jj3Uob{color:#0060f0;}.ob9lvb{color:#4d5156}.ob9lvb.HCMUuf{color:var(–IXoxUe)}.ylgVCe{color:#4d5156}.B6fmyf{position:absolute;top:0;height:0;visibility:hidden;white-space:nowrap;width:100%}.B6fmyf.Mg1HEd{height:auto}.ljeAnf{display:-webkit-box;overflow:hidden;-webkit-box-orient:vertical}
For example, you can use a regular expression to search for all occurrences of a phone number in a document, even if the phone numbers are written in different formats (e.g. "123-456-7890" or "(123) 456-7890"). This can be especially useful when working with large volumes of data.

.wDYxhc{clear:both}.cUnQKe .wDYxhc,.related-question-pair .wDYxhc,.M8OgIe .fm06If .wDYxhc{clear:none}html .dG2XIf .xpdclose .LKPcQc,html .dG2XIf .xpdopen .viOShc{padding-top:0;}.garHBe{color:var(–COEmY);font-size:20px;line-height:1.3;position:relative}.garHBe a{color:var(–COEmY)}.xpdopen .Hhmu2e{overflow:inherit}.xpdclose .a84NUc:not(:empty),.xpdopen .CQKTwc:not(:empty){border-top:solid 1px #ebebeb;border-radius:0}.xpdclose .pmYXee .a84NUc:not(:empty),.xpdopen .pmYXee .CQKTwc:not(:empty){border-top:none}.cAn2Qb .a84NUc:not(:empty),.cAn2Qb .CQKTwc:not(:empty){border-top:none}.SHa8ve{display:none}.xpdclose .TOfaBb.SHa8ve,.xpdopen .LL5J7d.SHa8ve{display:block}.rKR6H{padding-top:0.1px}.xpdclose .oHglmf,.xpdopen .xzPb7d{padding-bottom:16px}.xpdclose .kp-header .oHglmf,.xpdopen .kp-header .xzPb7d{padding-bottom:0}.c2xzTb .xpdclose .oHglmf,.c2xzTb .xpdopen .xzPb7d{padding-bottom:0}.HSryR .xpdclose .oHglmf,.HSryR .xpdopen .xzPb7d{padding-bottom:0}.Wnoohf .xpdopen .yp1CPe,.OJXvsb .xpdclose .siXlze{padding-bottom:16px}.Wnoohf .xpdopen .yp1CPe .xpdbox g-more-link{top:28px}.Wnoohf .xpdclose .wDYxhc.xsZWvb,.Wnoohf .xpdopen .wDYxhc.EfDVh{padding-bottom:0}.OJXvsb .xpdclose .wDYxhc.siXlze{padding-bottom:16px}#rhs .dG2XIf .xpdclose .LKPcQc,#rhs .dG2XIf .xpdopen .viOShc{padding-top:0}#rhs .Wnoohf .xpdopen .yp1CPe,#rhs .OJXvsb .xpdclose .siXlze{padding-bottom:15px}#rhs .Wnoohf .xpdclose .wDYxhc.xsZWvb,#rhs .Wnoohf .xpdopen .wDYxhc.EfDVh{padding-bottom:0}#rhs .Wnoohf .xpdclose .wDYxhc.xsZWvb.ecRggb,#rhs .Wnoohf .xpdopen .wDYxhc.EfDVh.ecRggb,#rhs .dG2XIf .ecRggb{padding-bottom:15px}.ecRggb{background-color:#fff;box-shadow:none;border:1px solid #dadce0;border-radius:8px;margin:0 0 16px 0}.tWSgNb .cAn2Qb{border-bottom:none}.IiOSLb .rsGxI.Ww4FFb,.Ww4FFb{background-color:var(–xhUGwc);border-radius:0px;border-width:0;box-shadow:none}.Ww4FFb .mnr-c:not(:empty),.mnr-c:not(:empty) .Ww4FFb,.Ww4FFb .Ww4FFb{box-shadow:none;margin-bottom:0px}.vt6azd{margin:0px 0px 8px}.vt6azd{margin:0px 0px 30px}.CBvvz{margin:-var(–sds-sys-measurement–space-sm) 0px 0px}.CBvvz{margin:-30px 0px 0px}.Jb0Zif .UiGGAb.ILfuVd,.ILfuVd{font-size:16px;line-height:24px;}.fm06If .ILfuVd.NA6bn,.c2xzTb .ILfuVd.duSGDe,.c2xzTb .ILfuVd.NA6bn.c3biWd{font-size:14px;line-height:1.58;}.c2xzTb .zloOqf{font-size:16px;margin-bottom:16px;margin-top:-8px;}.FLWspc{margin:16px}.LFYdN{font-size:16px;margin:16px}.trNcde .ILfuVd{color:var(–bbQxAb);font-family:Google Sans,arial,sans-serif;font-size:14px;line-height:22px}.HSryR .ILfuVd{line-height:1.5}.ss6qqb .ILfuVd,.ss6qqb .UiGGAb.ILfuVd{font-size:14px;line-height:22px}.c2xzTb .qLYAZd{margin:16px 16px 16px 0;}.d9FyLd{padding:0 0 10px}.hgKElc{padding:0 8px 0 0}.kX21rb{font-size:12px;line-height:1.34;display:inline-block;font-family:Google Sans,arial,sans-serif;padding-right:0;white-space:nowrap}.SPV4pd{display:flex;overflow-x:auto}.SPV4pd::-webkit-scrollbar{display:none}.Vjskue{margin-left:8px}.JT9o0,.ZnIJV{align-items:center;border:1px solid var(–mXZkqc);border-radius:16px;box-sizing:border-box;color:#1a73e8;cursor:pointer;display:flex;height:32px;margin-bottom:16px}.BkHX0d{font-family:Google Sans,arial,sans-serif-medium,sans-serif;font-size:14px;line-height:20px;padding-right:20px;text-align:center;white-space:nowrap}.xv1D5b{display:block;padding:0 8px 0 12px;width:18px;height:18px}.LGOjhe{overflow:hidden;padding-bottom:20px}.trNcde .LGOjhe{overflow:visible}.SALvLe .LGOjhe,.Jb0Zif .LGOjhe,.HSryR .LGOjhe,.IVvPP .LGOjhe{padding:0 0 10px;margin:10px 0 0 0}.s6JM6d .SALvLe .LGOjhe{margin-top:12px;}.s6JM6d .HSryR .LGOjhe{margin-top:12px;padding-bottom:20px}#res .Jb0Zif .qDOt0b h3,.IVvPP .qDOt0b h3{font-size:16px;line-height:1.375}.Jb0Zif .qDOt0b .iUh30,.IVvPP .qDOt0b .iUh30{font-size:14px;line-height:1.58}.IVvPP .qDOt0b{border-bottom:1px solid var(–gS5jXb);padding-bottom:6px}.rjOVwe.ILfuVd{font-size:16px;line-height:20px}.dG2XIf .rjOVwe{padding-top:22px;padding-bottom:0;margin-bottom:1px}.xWd7I{padding-top:12px;}.ILfuVd.NA6bn,.ILfuVd.duSGDe,.ILfuVd.UiGGAb,.IVvPP .ILfuVd{font-size:14px;line-height:22px}.n6SJS .ILfuVd{font-size:14px}.ILfuVd.NA6bn,.ILfuVd.duSGDe,.ILfuVd.UiGGAb,.IVvPP .ILfuVd{line-height:20px}.xpd-wa .g-blk{margin:initial}.xpd-wa .dG2XIf{border:initial;box-shadow:none}.fm06If .ILfuVd,.c2xzTb .ILfuVd,.Jb0Zif .c2xzTb .ILfuVd{font-family:Google Sans,arial,sans-serif;color:var(–YLNNHc)}.fm06If .ILfuVd,.c2xzTb .ILfuVd,.Jb0Zif .c2xzTb .ILfuVd{font-size:20px;line-height:28px}.cUnQKe .ILfuVd,.cUnQKe .UiGGAb.ILfuVd,.w5mTAe .ILfuVd,.W0urI .ILfuVd{color:var(–bbQxAb);font-family:Google Sans,arial,sans-serif;font-size:16px;line-height:24px}.fm06If .ILfuVd b,.trNcde .ILfuVd b,.cUnQKe .ILfuVd b,.c2xzTb .ILfuVd b,.w5mTAe .ILfuVd b,.W0urI .ILfuVd b{background-color:#d3e3fd;color:#040c28;font-weight:500}@media (forced-colors:active){.fm06If .ILfuVd b,.c2xzTb .ILfuVd b,.trNcde .ILfuVd b,.cUnQKe .ILfuVd b,.w5mTAe .ILfuVd b,.W0urI .ILfuVd b{background-color:Mark;color:MarkText}}.vBnbff .mO5MMe{padding-top:10px}.cUnQKe .vBnbff .mO5MMe{padding-left:0;}.trNcde .vBnbff .mO5MMe{padding:10px 0 0 0}.cAn2Qb.abzPbc .mnr-c{max-width:calc(100% – 162px)}.tF2Cxc{position:relative}.Jb0Zif .BDNLRc{margin:16px 16px -11px}.RUXr2d{display:inline}.MTB56{margin-right:12px;vertical-align:middle}.Pthbuf{display:flex;align-items:center}.m164Nd{vertical-align:middle;display:inline-block}.qpGQpf{clear:both;padding-top:6px}.aCOpRe{line-height:1.58;word-wrap:break-word}.aCOpRe sup{line-height:0.9}.yuRUbf{font-weight:normal;font-size:small;line-height:1.58;}.IsZvec{max-width:48em;color:#4d5156;line-height:1.58}.uo4vr{color:var(–IXoxUe);line-height:1.58}.IjZ7ze{display:inline-block;color:var(–IXoxUe);font-size:12px;line-height:1.34;white-space:nowrap}.FyYA1e{margin:5px 0}a:hover h3.LC20lb{text-decoration:underline}.M8OgIe .dG2XIf .fm06If .LC20lb,.n6SJS h3.LC20lb{overflow:hidden;text-overflow:ellipsis;white-space:nowrap;width:100%}.LC20lb{display:inline-block;line-height:1.3;margin-bottom:3px;}.c2xzTb .LC20lb{margin-bottom:0}.MMgsKf{padding-top:2px}.DKV0Md{padding-top:4px;padding-top:5px;}.Z3xoIb{padding-top:27px;padding-top:28px;}.NXKJM{display:-webkit-box;overflow:hidden;-webkit-box-orient:vertical;-webkit-line-clamp:1}.hceuRc{-webkit-box-orient:vertical;display:-webkit-box;-webkit-line-clamp:2;overflow:hidden}.fzBvHb{font-weight:700}.DKV0Md,.Z3xoIb{margin-top:18px;}.xvfwl{margin-top:4px}.q0vns a.fl{font-size:12px}.TQc1id .qLRx3b{font-size:14px;line-height:1.58}.HGLrXd{display:inline-block;-webkit-text-size-adjust:none}.q0vns{display:inline-block;padding-bottom:2px;padding-top:1px}.NJjxre{position:absolute;left:0;top:0;width:100%}.M8OgIe .VWCdhc.Mjve0e .q0vns{width:max-content}.VjDLd .TieM1d .tjvcx,.IVvPP .tjvcx,.kno-kp .tjvcx,.VjDLd .kp-wholepage-osrp .tjvcx,#rhs .ss6qqb .tjvcx,#rhs .trNcde .tjvcx{display:inline-block;height:19px;overflow-y:hidden}.ojE3Fb{padding:0;padding-bottom:0;}.ojE3Fb .q0vns{display:flex;overflow:hidden;padding:0;padding-bottom:0;align-items:center;}.ojE3Fb .q0vns a.fl{padding-top:0;font-size:12px;line-height:18px;}.GvPZzd{font-size:12px;line-height:18px;}.dTxz9{padding-right:38px}.iG7WGe{color:#202124;padding:0;text-align:center;width:16px}.VuuXrf{color:#202124;font-size:14px;display:block;line-height:20px;white-space:nowrap;}.qncq2c{font-size:12px;line-height:16px;margin-left:6px}.CA5RN{overflow:hidden}.K2VDSb{display:flex;flex-direction:row}.H9lube{background-color:#f1f3f4;border:1px solid #dadce0;border-radius:50%;display:inline-flex;justify-content:center;align-items:center;height:26px;width:26px;margin-right:12px;flex-shrink:0;vertical-align:middle;}.fJOpI.H9lube{background-color:#e2eeff;border:1px solid #e2eeff}.P1UpZb{background-color:#f1f3f4;border:1px solid #ecedef}.eqA2re.NjwKYd{margin-right:0}.Vwoesf:not(.oRVWZ){display:inline-block}.Vwoesf{vertical-align:middle}.XNo5Ab.XNo5Ab{display:block;}.lWlVCe{border-radius:50%}.bJVp8c{color:#0060f0}.Jj3Uob{color:#0060f0;}.ob9lvb{color:#4d5156}.ob9lvb.HCMUuf{color:var(–IXoxUe)}.ylgVCe{color:#4d5156}.B6fmyf{position:absolute;top:0;height:0;visibility:hidden;white-space:nowrap;width:100%}.B6fmyf.Mg1HEd{height:auto}.ljeAnf{display:-webkit-box;overflow:hidden;-webkit-box-orient:vertical}.byrV5b{align-items:center;display:
flex;flex-direction:row}.sBJG1d{display:flex;flex-direction:row;justify-content:center}.kDmHO{align-items:center;display:flex;flex-direction:column}.lR4vec{display:flex;flex-direction:column;justify-content:center}.xTEyc{align-items:start;display:flex;flex-direction:row}.OjFzvd{display:flex;flex-direction:row;justify-content:start}.YIPhrb{align-items:start;display:flex;flex-direction:column}.BToiNc{display:flex;flex-direction:column;justify-content:start}.E4bmEc .Va021{flex:1 1 100%}.E4bmEc .Y76LGf{flex:1 1 calc(50% – 4px)}
A regular expression is a pattern that the regular expression engine attempts to match in input text. A pattern consists of one or more character literals, operators, or constructs.

What are the rules for regular expression

.wDYxhc{clear:both}.cUnQKe .wDYxhc,.related-question-pair .wDYxhc,.M8OgIe .fm06If .wDYxhc{clear:none}html .dG2XIf .xpdclose .LKPcQc,html .dG2XIf .xpdopen .viOShc{padding-top:0;}.garHBe{color:var(–COEmY);font-size:20px;line-height:1.3;position:relative}.garHBe a{color:var(–COEmY)}.xpdopen .Hhmu2e{overflow:inherit}.xpdclose .a84NUc:not(:empty),.xpdopen .CQKTwc:not(:empty){border-top:solid 1px #ebebeb;border-radius:0}.xpdclose .pmYXee .a84NUc:not(:empty),.xpdopen .pmYXee .CQKTwc:not(:empty){border-top:none}.cAn2Qb .a84NUc:not(:empty),.cAn2Qb .CQKTwc:not(:empty){border-top:none}.SHa8ve{display:none}.xpdclose .TOfaBb.SHa8ve,.xpdopen .LL5J7d.SHa8ve{display:block}.rKR6H{padding-top:0.1px}.xpdclose .oHglmf,.xpdopen .xzPb7d{padding-bottom:16px}.xpdclose .kp-header .oHglmf,.xpdopen .kp-header .xzPb7d{padding-bottom:0}.c2xzTb .xpdclose .oHglmf,.c2xzTb .xpdopen .xzPb7d{padding-bottom:0}.HSryR .xpdclose .oHglmf,.HSryR .xpdopen .xzPb7d{padding-bottom:0}.Wnoohf .xpdopen .yp1CPe,.OJXvsb .xpdclose .siXlze{padding-bottom:16px}.Wnoohf .xpdopen .yp1CPe .xpdbox g-more-link{top:28px}.Wnoohf .xpdclose .wDYxhc.xsZWvb,.Wnoohf .xpdopen .wDYxhc.EfDVh{padding-bottom:0}.OJXvsb .xpdclose .wDYxhc.siXlze{padding-bottom:16px}#rhs .dG2XIf .xpdclose .LKPcQc,#rhs .dG2XIf .xpdopen .viOShc{padding-top:0}#rhs .Wnoohf .xpdopen .yp1CPe,#rhs .OJXvsb .xpdclose .siXlze{padding-bottom:15px}#rhs .Wnoohf .xpdclose .wDYxhc.xsZWvb,#rhs .Wnoohf .xpdopen .wDYxhc.EfDVh{padding-bottom:0}#rhs .Wnoohf .xpdclose .wDYxhc.xsZWvb.ecRggb,#rhs .Wnoohf .xpdopen .wDYxhc.EfDVh.ecRggb,#rhs .dG2XIf .ecRggb{padding-bottom:15px}.ecRggb{background-color:#fff;box-shadow:none;border:1px solid #dadce0;border-radius:8px;margin:0 0 16px 0}.tWSgNb .cAn2Qb{border-bottom:none}.Jb0Zif .UiGGAb.ILfuVd,.ILfuVd{font-size:16px;line-height:24px;}.fm06If .ILfuVd.NA6bn,.c2xzTb .ILfuVd.duSGDe,.c2xzTb .ILfuVd.NA6bn.c3biWd{font-size:14px;line-height:1.58;}.c2xzTb .zloOqf{font-size:16px;margin-bottom:16px;margin-top:-8px;}.FLWspc{margin:16px}.LFYdN{font-size:16px;margin:16px}.trNcde .ILfuVd{color:var(–bbQxAb);font-family:Google Sans,arial,sans-serif;font-size:14px;line-height:22px}.HSryR .ILfuVd{line-height:1.5}.ss6qqb .ILfuVd,.ss6qqb .UiGGAb.ILfuVd{font-size:14px;line-height:22px}.c2xzTb .qLYAZd{margin:16px 16px 16px 0;}.d9FyLd{padding:0 0 10px}.hgKElc{padding:0 8px 0 0}.kX21rb{font-size:12px;line-height:1.34;display:inline-block;font-family:Google Sans,arial,sans-serif;padding-right:0;white-space:nowrap}.SPV4pd{display:flex;overflow-x:auto}.SPV4pd::-webkit-scrollbar{display:none}.Vjskue{margin-left:8px}.JT9o0,.ZnIJV{align-items:center;border:1px solid var(–mXZkqc);border-radius:16px;box-sizing:border-box;color:#1a73e8;cursor:pointer;display:flex;height:32px;margin-bottom:16px}.BkHX0d{font-family:Google Sans,arial,sans-serif-medium,sans-serif;font-size:14px;line-height:20px;padding-right:20px;text-align:center;white-space:nowrap}.xv1D5b{display:block;padding:0 8px 0 12px;width:18px;height:18px}.LGOjhe{overflow:hidden;padding-bottom:20px}.trNcde .LGOjhe{overflow:visible}.SALvLe .LGOjhe,.Jb0Zif .LGOjhe,.HSryR .LGOjhe,.IVvPP .LGOjhe{padding:0 0 10px;margin:10px 0 0 0}.s6JM6d .SALvLe .LGOjhe{margin-top:12px;}.s6JM6d .HSryR .LGOjhe{margin-top:12px;padding-bottom:20px}#res .Jb0Zif .qDOt0b h3,.IVvPP .qDOt0b h3{font-size:16px;line-height:1.375}.Jb0Zif .qDOt0b .iUh30,.IVvPP .qDOt0b .iUh30{font-size:14px;line-height:1.58}.IVvPP .qDOt0b{border-bottom:1px solid var(–gS5jXb);padding-bottom:6px}.rjOVwe.ILfuVd{font-size:16px;line-height:20px}.dG2XIf .rjOVwe{padding-top:22px;padding-bottom:0;margin-bottom:1px}.xWd7I{padding-top:12px;}.ILfuVd.NA6bn,.ILfuVd.duSGDe,.ILfuVd.UiGGAb,.IVvPP .ILfuVd{font-size:14px;line-height:22px}.n6SJS .ILfuVd{font-size:14px}.ILfuVd.NA6bn,.ILfuVd.duSGDe,.ILfuVd.UiGGAb,.IVvPP .ILfuVd{line-height:20px}.xpd-wa .g-blk{margin:initial}.xpd-wa .dG2XIf{border:initial;box-shadow:none}.fm06If .ILfuVd,.c2xzTb .ILfuVd,.Jb0Zif .c2xzTb .ILfuVd{font-family:Google Sans,arial,sans-serif;color:var(–YLNNHc)}.fm06If .ILfuVd,.c2xzTb .ILfuVd,.Jb0Zif .c2xzTb .ILfuVd{font-size:20px;line-height:28px}.cUnQKe .ILfuVd,.cUnQKe .UiGGAb.ILfuVd,.w5mTAe .ILfuVd,.W0urI .ILfuVd{color:var(–bbQxAb);font-family:Google Sans,arial,sans-serif;font-size:16px;line-height:24px}.fm06If .ILfuVd b,.trNcde .ILfuVd b,.cUnQKe .ILfuVd b,.c2xzTb .ILfuVd b,.w5mTAe .ILfuVd b,.W0urI .ILfuVd b{background-color:#d3e3fd;color:#040c28;font-weight:500}@media (forced-colors:active){.fm06If .ILfuVd b,.c2xzTb .ILfuVd b,.trNcde .ILfuVd b,.cUnQKe .ILfuVd b,.w5mTAe .ILfuVd b,.W0urI .ILfuVd b{background-color:Mark;color:MarkText}}.vBnbff .mO5MMe{padding-top:10px}.cUnQKe .vBnbff .mO5MMe{padding-left:0;}.trNcde .vBnbff .mO5MMe{padding:10px 0 0 0}.cAn2Qb.abzPbc .mnr-c{max-width:calc(100% – 162px)}.tF2Cxc{position:relative}.Jb0Zif .BDNLRc{margin:16px 16px -11px}.RUXr2d{display:inline}.MTB56{margin-right:12px;vertical-align:middle}.Pthbuf{display:flex;align-items:center}.m164Nd{vertical-align:middle;display:inline-block}.qpGQpf{clear:both;padding-top:6px}.aCOpRe{line-height:1.58;word-wrap:break-word}.aCOpRe sup{line-height:0.9}.yuRUbf{font-weight:normal;font-size:small;line-height:1.58;}.IsZvec{max-width:48em;color:#4d5156;line-height:1.58}.uo4vr{color:var(–IXoxUe);line-height:1.58}.IjZ7ze{display:inline-block;color:var(–IXoxUe);font-size:12px;line-height:1.34;white-space:nowrap}.FyYA1e{margin:5px 0}a:hover h3.LC20lb{text-decoration:underline}.M8OgIe .dG2XIf .fm06If .LC20lb,.n6SJS h3.LC20lb{overflow:hidden;text-overflow:ellipsis;white-space:nowrap;width:100%}.LC20lb{display:inline-block;line-height:1.3;margin-bottom:3px;}.c2xzTb .LC20lb{margin-bottom:0}.MMgsKf{padding-top:2px}.DKV0Md{padding-top:4px;padding-top:5px;}.Z3xoIb{padding-top:27px;padding-top:28px;}.NXKJM{display:-webkit-box;overflow:hidden;-webkit-box-orient:vertical;-webkit-line-clamp:1}.hceuRc{-webkit-box-orient:vertical;display:-webkit-box;-webkit-line-clamp:2;overflow:hidden}.fzBvHb{font-weight:700}.DKV0Md,.Z3xoIb{margin-top:18px;}.xvfwl{margin-top:4px}.q0vns a.fl{font-size:12px}.TQc1id .qLRx3b{font-size:14px;line-height:1.58}.HGLrXd{display:inline-block;-webkit-text-size-adjust:none}.q0vns{display:inline-block;padding-bottom:2px;padding-top:1px}.NJjxre{position:absolute;left:0;top:0;width:100%}.M8OgIe .VWCdhc.Mjve0e .q0vns{width:max-content}.VjDLd .TieM1d .tjvcx,.IVvPP .tjvcx,.kno-kp .tjvcx,.VjDLd .kp-wholepage-osrp .tjvcx,#rhs .ss6qqb .tjvcx,#rhs .trNcde .tjvcx{display:inline-block;height:19px;overflow-y:hidden}.ojE3Fb{padding:0;padding-bottom:0;}.ojE3Fb .q0vns{display:flex;overflow:hidden;padding:0;padding-bottom:0;align-items:center;}.ojE3Fb .q0vns a.fl{padding-top:0;font-size:12px;line-height:18px;}.GvPZzd{font-size:12px;line-height:18px;}.dTxz9{padding-right:38px}.iG7WGe{color:#202124;padding:0;text-align:center;width:16px}.VuuXrf{color:#202124;font-size:14px;display:block;line-height:20px;white-space:nowrap;}.qncq2c{font-size:12px;line-height:16px;margin-left:6px}.CA5RN{overflow:hidden}.K2VDSb{display:flex;flex-direction:row}.H9lube{background-color:#f1f3f4;border:1px solid #dadce0;border-radius:50%;display:inline-flex;justify-content:center;align-items:center;height:26px;width:26px;margin-right:12px;flex-shrink:0;vertical-align:middle;}.fJOpI.H9lube{background-color:#e2eeff;border:1px solid #e2eeff}.P1UpZb{background-color:#f1f3f4;border:1px solid #ecedef}.eqA2re.NjwKYd{margin-right:0}.Vwoesf:not(.oRVWZ){display:inline-block}.Vwoesf{vertical-align:middle}.XNo5Ab.XNo5Ab{display:block;}.lWlVCe{border-radius:50%}.bJVp8c{color:#0060f0}.Jj3Uob{color:#0060f0;}.ob9lvb{color:#4d5156}.ob9lvb.HCMUuf{color:var(–IXoxUe)}.ylgVCe{color:#4d5156}.B6fmyf{position:absolute;top:0;height:0;visibility:hidden;white-space:nowrap;width:100%}.B6fmyf.Mg1HEd{height:auto}.ljeAnf{display:-webkit-box;overflow:hidden;-webkit-box-orient:vertical}
Regular expression can be defined by the following rules: Every letter of the alphabet ∑ is a regular expression. Null string є and empty set Φ are regular expressions. If a string can be derived from the rules 1, 2 and 3 then it is also a regular expression..wDYxhc{clear:both}.cUnQKe .wDYxhc,.related-question-pair .wDYxhc,.M8OgIe .fm06If .wDYxhc{clear:none}html .dG2XIf .xpdclose .LKPcQc,html .dG2XIf .xpdopen .viOShc{padding-top:0;}.garHBe{color:var(–COEmY);font-size:20px;line-height:1.3;position:relative}.garHBe a{color:var(–COEmY)}.xpdopen .Hhmu2e{overflow:inherit}.xpdclose .a84NUc:not(:empty),.xpdopen .CQKTwc:not(:empty){border-top:solid 1px #ebebeb;border-radius:0}.xpdclose .pmYXee .a84NUc:not(:empty),.xpdopen .pmYXee .CQKTwc:not(:empty){border-top:none}.cAn2Qb .a84NUc:not(:empty),.cAn2Qb .CQKTwc:not(:empty){border-top:none}.SHa8ve{display:none}.xpdclose .TOfaBb.SHa8ve,.xpdopen .LL5J7d.SHa8ve{display:block}.rKR6H{padding-top:0.1px}.xpdclose .oHglmf,.xpdopen .xzPb7d{padding-bottom:16px}.xpdclose .kp-header .oHglmf,.xpdopen .kp-header .xzPb7d{padding-bottom:0}.c2xzTb .xpdclose .oHglmf,.c2xzTb .xpdopen .xzPb7d{padding-bottom:0}.HSryR .xpdclose .oHglmf,.HSryR .xpdopen .xzPb7d{padding-bottom:0}.Wnoohf .xpdopen .yp1CPe,.OJXvsb .xpdclose .siXlze{padding-bottom:16px}.Wnoohf .xpdopen .yp1CPe .xpdbox g-more-link{top:28px}.Wnoohf .xpdclose .wDYxhc.xsZWvb,.Wnoohf .xpdopen .wDYxhc.EfDVh{padding-bottom:0}.OJXvsb .xpdclose .wDYxhc.siXlze{padding-bottom:16px}#rhs .dG2XIf .xpdclose .LKPcQc,#rhs .dG2XIf .xpdopen .viOShc{padding-top:0}#rhs .Wnoohf .xpdopen .yp1CPe,#rhs .OJXvsb .xpdclose .siXlze{padding-bottom:15px}#rhs .Wnoohf .xpdclose .wDYxhc.xsZWvb,#rhs .Wnoohf .xpdopen .wDYxhc.EfDVh{padding-bottom:0}#rhs .Wnoohf .xpdclose .wDYxhc.xsZWvb.ecRggb,#rhs .Wnoohf .xpdopen .wDYxhc.EfDVh.ecRggb,#rhs .dG2XIf .ecRggb{padding-bottom:15px}.ecRggb{background-color:#fff;box-shadow:none;border:1px solid #dadce0;border-radius:8px;margin:0 0 16px 0}.tWSgNb .cAn2Qb{border-bottom:none}.Jb0Zif .UiGGAb.ILfuVd,.ILfuVd{font-size:16px;line-height:24px;}.fm06If .ILfuVd.NA6bn,.c2xzTb .ILfuVd.duSGDe,.c2xzTb .ILfuVd.NA6bn.c3biWd{font-size:14px;line-height:1.58;}.c2xzTb .zloOqf{font-size:16px;margin-bottom:16px;margin-top:-8px;}.FLWspc{margin:16px}.LFYdN{font-size:16px;margin:16px}.trNcde .ILfuVd{color:var(–bbQxAb);font-family:Google Sans,arial,sans-serif;font-size:14px;line-height:22px}.HSryR .ILfuVd{line-height:1.5}.ss6qqb .ILfuVd,.ss6qqb .UiGGAb.ILfuVd{font-size:14px;line-height:22px}.c2xzTb .qLYAZd{margin:16px 16px 16px 0;}.d9FyLd{padding:0 0 10px}.hgKElc{padding:0 8px 0 0}.kX21rb{font-size:12px;line-height:1.34;display:inline-block;font-family:Google Sans,arial,sans-serif;padding-right:0;white-space:nowrap}.SPV4pd{display:flex;overflow-x:auto}.SPV4pd::-webkit-scrollbar{display:none}.Vjskue{margin-left:8px}.JT9o0,.ZnIJV{align-items:center;border:1px solid var(–mXZkqc);border-radius:16px;box-sizing:border-box;color:#1a73e8;cursor:pointer;display:flex;height:32px;margin-bottom:16px}.BkHX0d{font-family:Google Sans,arial,sans-serif-medium,sans-serif;font-size:14px;line-height:20px;padding-right:20px;text-align:center;white-space:nowrap}.xv1D5b{display:block;padding:0 8px 0 12px;width:18px;height:18px}.LGOjhe{overflow:hidden;padding-bottom:20px}.trNcde .LGOjhe{overflow:visible}.SALvLe .LGOjhe,.Jb0Zif .LGOjhe,.HSryR .LGOjhe,.IVvPP .LGOjhe{padding:0 0 10px;margin:10px 0 0 0}.s6JM6d .SALvLe .LGOjhe{margin-top:12px;}.s6JM6d .HSryR .LGOjhe{margin-top:12px;padding-bottom:20px}#res .Jb0Zif .qDOt0b h3,.IVvPP .qDOt0b h3{font-size:16px;line-height:1.375}.Jb0Zif .qDOt0b .iUh30,.IVvPP .qDOt0b .iUh30{font-size:14px;line-height:1.58}.IVvPP .qDOt0b{border-bottom:1px solid var(–gS5jXb);padding-bottom:6px}.rjOVwe.ILfuVd{font-size:16px;line-height:20px}.dG2XIf .rjOVwe{padding-top:22px;padding-bottom:0;margin-bottom:1px}.xWd7I{padding-top:12px;}.ILfuVd.NA6bn,.ILfuVd.duSGDe,.ILfuVd.UiGGAb,.IVvPP .ILfuVd{font-size:14px;line-height:22px}.n6SJS .ILfuVd{font-size:14px}.ILfuVd.NA6bn,.ILfuVd.duSGDe,.ILfuVd.UiGGAb,.IVvPP .ILfuVd{line-height:20px}.xpd-wa .g-blk{margin:initial}.xpd-wa .dG2XIf{border:initial;box-shadow:none}.fm06If .ILfuVd,.c2xzTb .ILfuVd,.Jb0Zif .c2xzTb .ILfuVd{font-family:Google Sans,arial,sans-serif;color:var(–YLNNHc)}.fm06If .ILfuVd,.c2xzTb .ILfuVd,.Jb0Zif .c2xzTb .ILfuVd{font-size:20px;line-height:28px}.cUnQKe .ILfuVd,.cUnQKe .UiGGAb.ILfuVd,.w5mTAe .ILfuVd,.W0urI .ILfuVd{color:var(–bbQxAb);font-family:Google Sans,arial,sans-serif;font-size:16px;line-height:24px}.fm06If .ILfuVd b,.trNcde .ILfuVd b,.cUnQKe .ILfuVd b,.c2xzTb .ILfuVd b,.w5mTAe .ILfuVd b,.W0urI .ILfuVd b{background-color:#d3e3fd;color:#040c28;font-weight:500}@media (forced-colors:active){.fm06If .ILfuVd b,.c2xzTb .ILfuVd b,.trNcde .ILfuVd b,.cUnQKe .ILfuVd b,.w5mTAe .ILfuVd b,.W0urI .ILfuVd b{background-color:Mark;color:MarkText}}.vBnbff .mO5MMe{padding-top:10px}.cUnQKe .vBnbff .mO5MMe{padding-left:0;}.trNcde .vBnbff .mO5MMe{padding:10px 0 0 0}.cAn2Qb.abzPbc .mnr-c{max-width:calc(100% – 162px)}.tF2Cxc{position:relative}.Jb0Zif .BDNLRc{margin:16px 16px -11px}.RUXr2d{display:inline}.MTB56{margin-right:12px;vertical-align:middle}.Pthbuf{display:flex;align-items:center}.m164Nd{vertical-align:middle;display:inline-block}.qpGQpf{clear:both;padding-top:6px}.aCOpRe{line-height:1.58;word-wrap:break-word}.aCOpRe sup{line-height:0.9}.yuRUbf{font-weight:normal;font-size:small;line-height:1.58;}.IsZvec{max-width:48em;color:#4d5156;line-height:1.58}.uo4vr{color:var(–IXoxUe);line-height:1.58}.IjZ7ze{display:inline-block;color:var(–IXoxUe);font-size:12px;line-height:1.34;white-space:nowrap}.FyYA1e{margin:5px 0}a:hover h3.LC20lb{text-decoration:underline}.M8OgIe .dG2XIf .fm06If .LC20lb,.n6SJS h3.LC20lb{overflow:hidden;text-overflow:ellipsis;white-space:nowrap;width:100%}.LC20lb{display:inline-block;line-height:1.3;margin-bottom:3px;}.c2xzTb .LC20lb{margin-bottom:0}.MMgsKf{padding-top:2px}.DKV0Md{padding-top:4px;padding-top:5px;}.Z3xoIb{padding-top:27px;padding-top:28px;}.NXKJM{display:-webkit-box;overflow:hidden;-webkit-box-orient:vertical;-webkit-line-clamp:1}.hceuRc{-webkit-box-orient:vertical;display:-webkit-box;-webkit-line-clamp:2;overflow:hidden}.fzBvHb{font-weight:700}.DKV0Md,.Z3xoIb{margin-top:18px;}.xvfwl{margin-top:4px}.q0vns a.fl{font-size:12px}.TQc1id .qLRx3b{font-size:14px;line-height:1.58}.HGLrXd{display:inline-block;-webkit-text-size-adjust:none}.q0vns{display:inline-block;padding-bottom:2px;padding-top:1px}.NJjxre{position:absolute;left:0;top:0;width:100%}.M8OgIe .VWCdhc.Mjve0e .q0vns{width:max-content}.VjDLd .TieM1d .tjvcx,.IVvPP .tjvcx,.kno-kp .tjvcx,.VjDLd .kp-wholepage-osrp .tjvcx,#rhs .ss6qqb .tjvcx,#rhs .trNcde .tjvcx{display:inline-block;height:19px;overflow-y:hidden}.ojE3Fb{padding:0;padding-bottom:0;}.ojE3Fb .q0vns{display:flex;overflow:hidden;padding:0;padding-bottom:0;align-items:center;}.ojE3Fb .q0vns a.fl{padding-top:0;font-size:12px;line-height:18px;}.GvPZzd{font-size:12px;line-height:18px;}.dTxz9{padding-right:38px}.iG7WGe{color:#202124;padding:0;text-align:center;width:16px}.VuuXrf{color:#202124;font-size:14px;display:block;line-height:20px;white-space:nowrap;}.qncq2c{font-size:12px;line-height:16px;margin-left:6px}.CA5RN{overflow:hidden}.K2VDSb{display:flex;flex-direction:row}.H9lube{background-color:#f1f3f4;border:1px solid #dadce0;border-radius:50%;display:inline-flex;justify-content:center;align-items:center;height:26px;width:26px;margin-right:12px;flex-shrink:0;vertical-align:middle;}.fJOpI.H9lube{background-color:#e2eeff;border:1px solid #e2eeff}.P1UpZb{background-color:#f1f3f4;border:1px solid #ecedef}.eqA2re.NjwKYd{margin-right:0}.Vwoesf:not(.oRVWZ){display:inline-block}.Vwoesf{vertical-align:middle}.XNo5Ab.XNo5Ab{display:block;}.lWlVCe{border-radius:50%}.bJVp8c{color:#0060f0}.Jj3Uob{color:#0060f0;}.ob9lvb{color:#4d5156}.ob9lvb.HCMUuf{color:var(–IXoxUe)}.ylgVCe{color:#4d5156}.B6fmyf{position:absolute;top:0;height:0;visibility:hidden;white-space:nowrap;width:100%}.B6fmyf.Mg1HEd{height:auto}.ljeAnf{display:-webkit-box;overflow:hidden;-webkit-box-orient:vertical}
In brief, regexes are hard. 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ce:nowrap;width:100%}.B6fmyf.Mg1HEd{height:auto}.ljeAnf{display:-webkit-box;overflow:hidden;-webkit-box-orient:vertical}.byrV5b{align-items:center;display:flex;flex-direction:row}.sBJG1d{display:flex;flex-direction:row;justify-content:center}.kDmHO{align-items:center;display:flex;flex-direction:column}.lR4vec{display:flex;flex-direction:column;justify-content:center}.xTEyc{align-items:start;display:flex;flex-direction:row}.OjFzvd{display:flex;flex-direction:row;justify-content:start}.YIPhrb{align-items:start;display:flex;flex-direction:column}.BToiNc{display:flex;flex-direction:column;justify-content:start}.E4bmEc .Va021{flex:1 1 100%}.E4bmEc .Y76LGf{flex:1 1 calc(50% – 4px)}
.* matches any character (except newline unless re.DOTALL flag is set) zero or more times. (.) captures a character. \1 backreference to the captured character. for example, if (.)

.wDYxhc{clear:both}.cUnQKe .wDYxhc,.related-question-pair .wDYxhc,.M8OgIe .fm06If .wDYxhc{clear:none}html .dG2XIf .xpdclose .LKPcQc,html .dG2XIf .xpdopen .viOShc{padding-top:0;}.garHBe{color:var(–COEmY);font-size:20px;line-height:1.3;position:relative}.garHBe a{color:var(–COEmY)}.xpdopen .Hhmu2e{overflow:inherit}.xpdclose .a84NUc:not(:empty),.xpdopen .CQKTwc:not(:empty){border-top:solid 1px #ebebeb;border-radius:0}.xpdclose .pmYXee .a84NUc:not(:empty),.xpdopen .pmYXee .CQKTwc:not(:empty){border-top:none}.cAn2Qb .a84NUc:not(:empty),.cAn2Qb .CQKTwc:not(:empty){border-top:none}.SHa8ve{display:none}.xpdclose .TOfaBb.SHa8ve,.xpdopen .LL5J7d.SHa8ve{display:block}.rKR6H{padding-top:0.1px}.xpdclose .oHglmf,.xpdopen .xzPb7d{padding-bottom:16px}.xpdclose .kp-header .oHglmf,.xpdopen .kp-header .xzPb7d{padding-bottom:0}.c2xzTb .xpdclose .oHglmf,.c2xzTb .xpdopen .xzPb7d{padding-bottom:0}.HSryR .xpdclose .oHglmf,.HSryR .xpdopen .xzPb7d{padding-bottom:0}.Wnoohf .xpdopen .yp1CPe,.OJXvsb .xpdclose .siXlze{padding-bottom:16px}.Wnoohf .xpdopen .yp1CPe .xpdbox g-more-link{top:28px}.Wnoohf .xpdclose .wDYxhc.xsZWvb,.Wnoohf .xpdopen .wDYxhc.EfDVh{padding-bottom:0}.OJXvsb .xpdclose .wDYxhc.siXlze{padding-bottom:16px}#rhs .dG2XIf .xpdclose .LKPcQc,#rhs .dG2XIf .xpdopen .viOShc{padding-top:0}#rhs .Wnoohf .xpdopen .yp1CPe,#rhs .OJXvsb .xpdclose .siXlze{padding-bottom:15px}#rhs .Wnoohf .xpdclose .wDYxhc.xsZWvb,#rhs .Wnoohf .xpdopen .wDYxhc.EfDVh{padding-bottom:0}#rhs .Wnoohf .xpdclose .wDYxhc.xsZWvb.ecRggb,#rhs .Wnoohf .xpdopen .wDYxhc.EfDVh.ecRggb,#rhs .dG2XIf .ecRggb{padding-bottom:15px}.ecRggb{background-color:#fff;box-shadow:none;border:1px solid #dadce0;border-radius:8px;margin:0 0 16px 0}.tWSgNb .cAn2Qb{border-bottom:none}.Jb0Zif .UiGGAb.ILfuVd,.ILfuVd{font-size:16px;line-height:24px;}.fm06If .ILfuVd.NA6bn,.c2xzTb .ILfuVd.duSGDe,.c2xzTb .ILfuVd.NA6bn.c3biWd{font-size:14px;line-height:1.58;}.c2xzTb .zloOqf{font-size:16px;margin-bottom:16px;margin-top:-8px;}.FLWspc{margin:16px}.LFYdN{font-size:16px;margin:16px}.trNcde .ILfuVd{color:var(–bbQxAb);font-family:Google Sans,arial,sans-serif;font-size:14px;line-height:22px}.HSryR .ILfuVd{line-height:1.5}.ss6qqb .ILfuVd,.ss6qqb .UiGGAb.ILfuVd{font-size:14px;line-height:22px}.c2xzTb .qLYAZd{margin:16px 16px 16px 0;}.d9FyLd{padding:0 0 10px}.hgKElc{padding:0 8px 0 0}.kX21rb{font-size:12px;line-height:1.34;display:inline-block;font-family:Google Sans,arial,sans-serif;padding-right:0;white-space:nowrap}.SPV4pd{display:flex;overflow-x:auto}.SPV4pd::-webkit-scrollbar{display:none}.Vjskue{margin-left:8px}.JT9o0,.ZnIJV{align-items:center;border:1px solid var(–mXZkqc);border-radius:16px;box-sizing:border-box;color:#1a73e8;cursor:pointer;display:flex;height:32px;margin-bottom:16px}.BkHX0d{font-family:Google Sans,arial,sans-serif-medium,sans-serif;font-size:14px;line-height:20px;padding-right:20px;text-align:center;white-space:nowrap}.xv1D5b{display:block;padding:0 8px 0 12px;width:18px;height:18px}.LGOjhe{overflow:hidden;padding-bottom:20px}.trNcde .LGOjhe{overflow:visible}.SALvLe .LGOjhe,.Jb0Zif .LGOjhe,.HSryR .LGOjhe,.IVvPP .LGOjhe{padding:0 0 10px;margin:10px 0 0 0}.s6JM6d .SALvLe .LGOjhe{margin-top:12px;}.s6JM6d .HSryR .LGOjhe{margin-top:12px;padding-bottom:20px}#res .Jb0Zif .qDOt0b h3,.IVvPP .qDOt0b h3{font-size:16px;line-height:1.375}.Jb0Zif .qDOt0b .iUh30,.IVvPP .qDOt0b .iUh30{font-size:14px;line-height:1.58}.IVvPP .qDOt0b{border-bottom:1px solid var(–gS5jXb);padding-bottom:6px}.rjOVwe.ILfuVd{font-size:16px;line-height:20px}.dG2XIf .rjOVwe{padding-top:22px;padding-bottom:0;margin-bottom:1px}.xWd7I{padding-top:12px;}.ILfuVd.NA6bn,.ILfuVd.duSGDe,.ILfuVd.UiGGAb,.IVvPP .ILfuVd{font-size:14px;line-height:22px}.n6SJS .ILfuVd{font-size:14px}.ILfuVd.NA6bn,.ILfuVd.duSGDe,.ILfuVd.UiGGAb,.IVvPP .ILfuVd{line-height:20px}.xpd-wa .g-blk{margin:initial}.xpd-wa .dG2XIf{border:initial;box-shadow:none}.fm06If .ILfuVd,.c2xzTb .ILfuVd,.Jb0Zif .c2xzTb .ILfuVd{font-family:Google Sans,arial,sans-serif;color:var(–YLNNHc)}.fm06If .ILfuVd,.c2xzTb .ILfuVd,.Jb0Zif .c2xzTb .ILfuVd{font-size:20px;line-height:28px}.cUnQKe .ILfuVd,.cUnQKe .UiGGAb.ILfuVd,.w5mTAe .ILfuVd,.W0urI .ILfuVd{color:var(–bbQxAb);font-family:Google Sans,arial,sans-serif;font-size:16px;line-height:24px}.fm06If .ILfuVd b,.trNcde .ILfuVd b,.cUnQKe .ILfuVd b,.c2xzTb .ILfuVd b,.w5mTAe .ILfuVd b,.W0urI .ILfuVd b{background-color:#d3e3fd;color:#040c28;font-weight:500}@media (forced-colors:active){.fm06If .ILfuVd b,.c2xzTb .ILfuVd b,.trNcde .ILfuVd b,.cUnQKe .ILfuVd b,.w5mTAe .ILfuVd b,.W0urI .ILfuVd b{background-color:Mark;color:MarkText}}.vBnbff .mO5MMe{padding-top:10px}.cUnQKe .vBnbff .mO5MMe{padding-left:0;}.trNcde .vBnbff .mO5MMe{padding:10px 0 0 0}.cAn2Qb.abzPbc .mnr-c{max-width:calc(100% – 162px)}.tF2Cxc{position:relative}.Jb0Zif .BDNLRc{margin:16px 16px -11px}.RUXr2d{display:inline}.MTB56{margin-right:12px;vertical-align:middle}.Pthbuf{display:flex;align-items:center}.m164Nd{vertical-align:middle;display:inline-block}.qpGQpf{clear:both;padding-top:6px}.aCOpRe{line-height:1.58;word-wrap:break-word}.aCOpRe sup{line-height:0.9}.yuRUbf{font-weight:normal;font-size:small;line-height:1.58;}.IsZvec{max-width:48em;color:#4d5156;line-height:1.58}.uo4vr{color:var(–IXoxUe);line-height:1.58}.IjZ7ze{display:inline-block;color:var(–IXoxUe);font-size:12px;line-height:1.34;white-space:nowrap}.FyYA1e{margin:5px 0}a:hover h3.LC20lb{text-decoration:underline}.M8OgIe .dG2XIf .fm06If .LC20lb,.n6SJS h3.LC20lb{overflow:hidden;text-overflow:ellipsis;white-space:nowrap;width:100%}.LC20lb{display:inline-block;line-height:1.3;margin-bottom:3px;}.c2xzTb .LC20lb{margin-bottom:0}.MMgsKf{padding-top:2px}.DKV0Md{padding-top:4px;padding-top:5px;}.Z3xoIb{padding-top:27px;padding-top:28px;}.NXKJM{display:-webkit-box;overflow:hidden;-webkit-box-orient:vertical;-webkit-line-clamp:1}.hceuRc{-webkit-box-orient:vertical;display:-webkit-box;-webkit-line-clamp:2;overflow:hidden}.fzBvHb{font-weight:700}.DKV0Md,.Z3xoIb{margin-top:18px;}.xvfwl{margin-top:4px}.q0vns a.fl{font-size:12px}.TQc1id .qLRx3b{font-size:14px;line-height:1.58}.HGLrXd{display:inline-block;-webkit-text-size-adjust:none}.q0vns{display:inline-block;padding-bottom:2px;padding-top:1px}.NJjxre{position:absolute;left:0;top:0;width:100%}.M8OgIe .VWCdhc.Mjve0e .q0vns{width:max-content}.VjDLd .TieM1d .tjvcx,.IVvPP .tjvcx,.kno-kp .tjvcx,.VjDLd .kp-wholepage-osrp .tjvcx,#rhs .ss6qqb .tjvcx,#rhs .trNcde .tjvcx{display:inline-block;height:19px;overflow-y:hidden}.ojE3Fb{padding:0;padding-bottom:0;}.ojE3Fb .q0vns{display:flex;overflow:hidden;padding:0;padding-bottom:0;align-items:center;}.ojE3Fb .q0vns a.fl{padding-top:0;font-size:12px;line-height:18px;}.GvPZzd{font-size:12px;line-height:18px;}.dTxz9{padding-right:38px}.iG7WGe{color:#202124;padding:0;text-align:center;width:16px}.VuuXrf{color:#202124;font-size:14px;display:block;line-height:20px;white-space:nowrap;}.qncq2c{font-size:12px;line-height:16px;margin-left:6px}.CA5RN{overflow:hidden}.K2VDSb{display:flex;flex-direction:row}.H9lube{background-color:#f1f3f4;border:1px solid #dadce0;border-radius:50%;display:inline-flex;justify-content:center;align-items:center;height:26px;width:26px;margin-right:12px;flex-shrink:0;vertical-align:middle;}.fJOpI.H9lube{background-color:#e2eeff;border:1px solid #e2eeff}.P1UpZb{background-color:#f1f3f4;border:1px solid #ecedef}.eqA2re.NjwKYd{margin-right:0}.Vwoesf:not(.oRVWZ){display:inline-block}.Vwoesf{vertical-align:middle}.XNo5Ab.XNo5Ab{display:block;}.lWlVCe{border-radius:50%}.bJVp8c{color:#0060f0}.Jj3Uob{color:#0060f0;}.ob9lvb{color:#4d5156}.ob9lvb.HCMUuf{color:var(–IXoxUe)}.ylgVCe{color:#4d5156}.B6fmyf{position:absolute;top:0;height:0;visibility:hidden;white-space:nowrap;width:100%}.B6fmyf.Mg1HEd{height:auto}.ljeAnf{display:-webkit-box;overflow:hidden;-webkit-box-orient:vertical}
Use curly braces ( {} ) when you want to be very specific about the number of occurrences an operator or subexpression must match in the source string. Curly braces and their contents are known as interval expressions. You can specify an exact number or a range, using any of the forms shown in Table 1-6.

How to interpret regular expressions : .wDYxhc{clear:both}.cUnQKe .wDYxhc,.related-question-pair .wDYxhc,.M8OgIe .fm06If .wDYxhc{clear:none}html .dG2XIf .xpdclose .LKPcQc,html .dG2XIf .xpdopen .viOShc{padding-top:0;}.garHBe{color:var(–COEmY);font-size:20px;line-height:1.3;position:relative}.garHBe a{color:var(–COEmY)}.xpdopen .Hhmu2e{overflow:inherit}.xpdclose .a84NUc:not(:empty),.xpdopen .CQKTwc:not(:empty){border-top:solid 1px #ebebeb;border-radius:0}.xpdclose .pmYXee .a84NUc:not(:empty),.xpdopen .pmYXee .CQKTwc:not(:empty){border-top:none}.cAn2Qb .a84NUc:not(:empty),.cAn2Qb .CQKTwc:not(:empty){border-top:none}.SHa8ve{display:none}.xpdclose .TOfaBb.SHa8ve,.xpdopen .LL5J7d.SHa8ve{display:block}.rKR6H{padding-top:0.1px}.xpdclose .oHglmf,.xpdopen .xzPb7d{padding-bottom:16px}.xpdclose .kp-header .oHglmf,.xpdopen .kp-header .xzPb7d{padding-bottom:0}.c2xzTb .xpdclose .oHglmf,.c2xzTb .xpdopen .xzPb7d{padding-bottom:0}.HSryR .xpdclose .oHglmf,.HSryR .xpdopen .xzPb7d{padding-bottom:0}.Wnoohf .xpdopen .yp1CPe,.OJXvsb .xpdclose .siXlze{padding-bottom:16px}.Wnoohf .xpdopen .yp1CPe .xpdbox g-more-link{top:28px}.Wnoohf .xpdclose .wDYxhc.xsZWvb,.Wnoohf .xpdopen .wDYxhc.EfDVh{padding-bottom:0}.OJXvsb .xpdclose .wDYxhc.siXlze{padding-bottom:16px}#rhs .dG2XIf .xpdclose .LKPcQc,#rhs .dG2XIf .xpdopen .viOShc{padding-top:0}#rhs .Wnoohf .xpdopen .yp1CPe,#rhs .OJXvsb .xpdclose .siXlze{padding-bottom:15px}#rhs .Wnoohf .xpdclose .wDYxhc.xsZWvb,#rhs .Wnoohf .xpdopen .wDYxhc.EfDVh{padding-bottom:0}#rhs .Wnoohf .xpdclose .wDYxhc.xsZWvb.ecRggb,#rhs .Wnoohf .xpdopen .wDYxhc.EfDVh.ecRggb,#rhs .dG2XIf .ecRggb{padding-bottom:15px}.ecRggb{background-color:#fff;box-shadow:none;border:1px solid #dadce0;border-radius:8px;margin:0 0 16px 0}.tWSgNb .cAn2Qb{border-bottom:none}.IiOSLb .rsGxI.Ww4FFb,.Ww4FFb{background-color:var(–xhUGwc);border-radius:0px;border-width:0;box-shadow:none}.Ww4FFb .mnr-c:not(:empty),.mnr-c:not(:empty) .Ww4FFb,.Ww4FFb .Ww4FFb{box-shadow:none;margin-bottom:0px}.vt6azd{margin:0px 0px 8px}.vt6azd{margin:0px 0px 30px}.CBvvz{margin:-var(–sds-sys-measurement–space-sm) 0px 0px}.CBvvz{margin:-30px 0px 0px}.Jb0Zif .UiGGAb.ILfuVd,.ILfuVd{font-size:16px;line-height:24px;}.fm06If .ILfuVd.NA6bn,.c2xzTb .ILfuVd.duSGDe,.c2xzTb .ILfuVd.NA6bn.c3biWd{font-size:14px;line-height:1.58;}.c2xzTb .zloOqf{font-size:16px;margin-bottom:16px;margin-top:-8px;}.FLWspc{margin:16px}.LFYdN{font-size:16px;margin:16px}.trNcde .ILfuVd{color:var(–bbQxAb);font-family:Google Sans,arial,sans-serif;font-size:14px;line-height:22px}.HSryR .ILfuVd{line-height:1.5}.ss6qqb .ILfuVd,.ss6qqb .UiGGAb.ILfuVd{font-size:14px;line-height:22px}.c2xzTb .qLYAZd{margin:16px 16px 16px 0;}.d9FyLd{padding:0 0 10px}.hgKElc{padding:0 8px 0 0}.kX21rb{font-size:12px;line-height:1.34;display:inline-block;font-family:Google Sans,arial,sans-serif;padding-right:0;white-space:nowrap}.SPV4pd{display:flex;overflow-x:auto}.SPV4pd::-webkit-scrollbar{display:none}.Vjskue{margin-left:8px}.JT9o0,.ZnIJV{align-items:center;border:1px solid var(–mXZkqc);border-radius:16px;box-sizing:border-box;color:#1a73e8;cursor:pointer;display:flex;height:32px;margin-bottom:16px}.BkHX0d{font-family:Google Sans,arial,sans-serif-medium,sans-serif;font-size:14px;line-height:20px;padding-right:20px;text-align:center;white-space:nowrap}.xv1D5b{display:block;padding:0 8px 0 12px;width:18px;height:18px}.LGOjhe{overflow:hidden;padding-bottom:20px}.trNcde .LGOjhe{overflow:visible}.SALvLe .LGOjhe,.Jb0Zif .LGOjhe,.HSryR .LGOjhe,.IVvPP .LGOjhe{padding:0 0 10px;margin:10px 0 0 0}.s6JM6d .SALvLe .LGOjhe{margin-top:12px;}.s6JM6d .HSryR .LGOjhe{margin-top:12px;padding-bottom:20px}#res .Jb0Zif .qDOt0b h3,.IVvPP .qDOt0b h3{font-size:16px;line-height:1.375}.Jb0Zif .qDOt0b .iUh30,.IVvPP .qDOt0b .iUh30{font-size:14px;line-height:1.58}.IVvPP .qDOt0b{border-bottom:1px solid var(–gS5jXb);padding-bottom:6px}.rjOVwe.ILfuVd{font-size:16px;line-height:20px}.dG2XIf .rjOVwe{padding-top:22px;padding-bottom:0;margin-bottom:1px}.xWd7I{padding-top:12px;}.ILfuVd.NA6bn,.ILfuVd.duSGDe,.ILfuVd.UiGGAb,.IVvPP .ILfuVd{font-size:14px;line-height:22px}.n6SJS .ILfuVd{font-size:14px}.ILfuVd.NA6bn,.ILfuVd.duSGDe,.ILfuVd.UiGGAb,.IVvPP .ILfuVd{line-height:20px}.xpd-wa .g-blk{margin:initial}.xpd-wa .dG2XIf{border:initial;box-shadow:none}.fm06If .ILfuVd,.c2xzTb .ILfuVd,.Jb0Zif .c2xzTb .ILfuVd{font-family:Google Sans,arial,sans-serif;color:var(–YLNNHc)}.fm06If .ILfuVd,.c2xzTb .ILfuVd,.Jb0Zif .c2xzTb .ILfuVd{font-size:20px;line-height:28px}.cUnQKe .ILfuVd,.cUnQKe .UiGGAb.ILfuVd,.w5mTAe .ILfuVd,.W0urI .ILfuVd{color:var(–bbQxAb);font-family:Google Sans,arial,sans-serif;font-size:16px;line-height:24px}.fm06If .ILfuVd b,.trNcde .ILfuVd b,.cUnQKe .ILfuVd b,.c2xzTb .ILfuVd b,.w5mTAe .ILfuVd b,.W0urI .ILfuVd b{background-color:#d3e3fd;color:#040c28;font-weight:500}@media (forced-colors:active){.fm06If .ILfuVd b,.c2xzTb .ILfuVd b,.trNcde .ILfuVd b,.cUnQKe .ILfuVd b,.w5mTAe .ILfuVd b,.W0urI .ILfuVd b{background-color:Mark;color:MarkText}}.vBnbff .mO5MMe{padding-top:10px}.cUnQKe .vBnbff .mO5MMe{padding-left:0;}.trNcde .vBnbff .mO5MMe{padding:10px 0 0 0}.cAn2Qb.abzPbc .mnr-c{max-width:calc(100% – 162px)}.tF2Cxc{position:relative}.Jb0Zif .BDNLRc{margin:16px 16px -11px}.RUXr2d{display:inline}.MTB56{margin-right:12px;vertical-align:middle}.Pthbuf{display:flex;align-items:center}.m164Nd{vertical-align:middle;display:inline-block}.qpGQpf{clear:both;padding-top:6px}.aCOpRe{line-height:1.58;word-wrap:break-word}.aCOpRe sup{line-height:0.9}.yuRUbf{font-weight:normal;font-size:small;line-height:1.58;}.IsZvec{max-width:48em;color:#4d5156;line-height:1.58}.uo4vr{color:var(–IXoxUe);line-height:1.58}.IjZ7ze{display:inline-block;color:var(–IXoxUe);font-size:12px;line-height:1.34;white-space:nowrap}.FyYA1e{margin:5px 0}a:hover h3.LC20lb{text-decoration:underline}.M8OgIe .dG2XIf .fm06If .LC20lb,.n6SJS h3.LC20lb{overflow:hidden;text-overflow:ellipsis;white-space:nowrap;width:100%}.LC20lb{display:inline-block;line-height:1.3;margin-bottom:3px;}.c2xzTb .LC20lb{margin-bottom:0}.MMgsKf{padding-top:2px}.DKV0Md{padding-top:4px;padding-top:5px;}.Z3xoIb{padding-top:27px;padding-top:28px;}.NXKJM{display:-webkit-box;overflow:hidden;-webkit-box-orient:vertical;-webkit-line-clamp:1}.hceuRc{-webkit-box-orient:vertical;display:-webkit-box;-webkit-line-clamp:2;overflow:hidden}.fzBvHb{font-weight:700}.DKV0Md,.Z3xoIb{margin-top:18px;}.xvfwl{margin-top:4px}.q0vns a.fl{font-size:12px}.TQc1id .qLRx3b{font-size:14px;line-height:1.58}.HGLrXd{display:inline-block;-webkit-text-size-adjust:none}.q0vns{display:inline-block;padding-bottom:2px;padding-top:1px}.NJjxre{position:absolute;left:0;top:0;width:100%}.M8OgIe .VWCdhc.Mjve0e .q0vns{width:max-content}.VjDLd .TieM1d .tjvcx,.IVvPP .tjvcx,.kno-kp .tjvcx,.VjDLd .kp-wholepage-osrp .tjvcx,#rhs .ss6qqb .tjvcx,#rhs .trNcde .tjvcx{display:inline-block;height:19px;overflow-y:hidden}.ojE3Fb{padding:0;padding-bottom:0;}.ojE3Fb .q0vns{display:flex;overflow:hidden;padding:0;padding-bottom:0;align-items:center;}.ojE3Fb .q0vns a.fl{padding-top:0;font-size:12px;line-height:18px;}.GvPZzd{font-size:12px;line-height:18px;}.dTxz9{padding-right:38px}.iG7WGe{color:#202124;padding:0;text-align:center;width:16px}.VuuXrf{color:#202124;font-size:14px;display:block;line-height:20px;white-space:nowrap;}.qncq2c{font-size:12px;line-height:16px;margin-left:6px}.CA5RN{overflow:hidden}.K2VDSb{display:flex;flex-direction:row}.H9lube{background-color:#f1f3f4;border:1px solid #dadce0;border-radius:50%;display:inline-flex;justify-content:center;align-items:center;height:26px;width:26px;margin-right:12px;flex-shrink:0;vertical-align:middle;}.fJOpI.H9lube{background-color:#e2eeff;border:1px solid #e2eeff}.P1UpZb{background-color:#f1f3f4;border:1px solid #ecedef}.eqA2re.NjwKYd{margin-right:0}.Vwoesf:not(.oRVWZ){display:inline-block}.Vwoesf{vertical-align:middle}.XNo5Ab.XNo5Ab{display:block;}.lWlVCe{border-radius:50%}
.bJVp8c{color:#0060f0}.Jj3Uob{color:#0060f0;}.ob9lvb{color:#4d5156}.ob9lvb.HCMUuf{color:var(–IXoxUe)}.ylgVCe{color:#4d5156}.B6fmyf{position:absolute;top:0;height:0;visibility:hidden;white-space:nowrap;width:100%}.B6fmyf.Mg1HEd{height:auto}.ljeAnf{display:-webkit-box;overflow:hidden;-webkit-box-orient:vertical}.byrV5b{align-items:center;display:flex;flex-direction:row}.sBJG1d{display:flex;flex-direction:row;justify-content:center}.kDmHO{align-items:center;display:flex;flex-direction:column}.lR4vec{display:flex;flex-direction:column;justify-content:center}.xTEyc{align-items:start;display:flex;flex-direction:row}.OjFzvd{display:flex;flex-direction:row;justify-content:start}.YIPhrb{align-items:start;display:flex;flex-direction:column}.BToiNc{display:flex;flex-direction:column;justify-content:start}.E4bmEc .Va021{flex:1 1 100%}.E4bmEc .Y76LGf{flex:1 1 calc(50% – 4px)}
Regular expressions start with a forward slash / followed by the pattern we want to match, and another forward slash / to end it. In this first example, we want to match a simple pattern: "dog". Our RegEx will highlight the first pattern it matches, which is the bold character in there.

Why do we use regular expressions : .wDYxhc{clear:both}.cUnQKe .wDYxhc,.related-question-pair .wDYxhc,.M8OgIe .fm06If .wDYxhc{clear:none}html .dG2XIf .xpdclose .LKPcQc,html .dG2XIf .xpdopen .viOShc{padding-top:0;}.garHBe{color:var(–COEmY);font-size:20px;line-height:1.3;position:relative}.garHBe a{color:var(–COEmY)}.xpdopen .Hhmu2e{overflow:inherit}.xpdclose .a84NUc:not(:empty),.xpdopen .CQKTwc:not(:empty){border-top:solid 1px #ebebeb;border-radius:0}.xpdclose .pmYXee .a84NUc:not(:empty),.xpdopen .pmYXee .CQKTwc:not(:empty){border-top:none}.cAn2Qb .a84NUc:not(:empty),.cAn2Qb .CQKTwc:not(:empty){border-top:none}.SHa8ve{display:none}.xpdclose .TOfaBb.SHa8ve,.xpdopen .LL5J7d.SHa8ve{display:block}.rKR6H{padding-top:0.1px}.xpdclose .oHglmf,.xpdopen .xzPb7d{padding-bottom:16px}.xpdclose .kp-header .oHglmf,.xpdopen .kp-header .xzPb7d{padding-bottom:0}.c2xzTb .xpdclose .oHglmf,.c2xzTb .xpdopen .xzPb7d{padding-bottom:0}.HSryR .xpdclose .oHglmf,.HSryR .xpdopen .xzPb7d{padding-bottom:0}.Wnoohf .xpdopen .yp1CPe,.OJXvsb .xpdclose .siXlze{padding-bottom:16px}.Wnoohf .xpdopen .yp1CPe .xpdbox g-more-link{top:28px}.Wnoohf .xpdclose .wDYxhc.xsZWvb,.Wnoohf .xpdopen .wDYxhc.EfDVh{padding-bottom:0}.OJXvsb .xpdclose .wDYxhc.siXlze{padding-bottom:16px}#rhs .dG2XIf .xpdclose .LKPcQc,#rhs .dG2XIf .xpdopen .viOShc{padding-top:0}#rhs .Wnoohf .xpdopen .yp1CPe,#rhs .OJXvsb .xpdclose .siXlze{padding-bottom:15px}#rhs .Wnoohf .xpdclose .wDYxhc.xsZWvb,#rhs .Wnoohf .xpdopen .wDYxhc.EfDVh{padding-bottom:0}#rhs .Wnoohf .xpdclose .wDYxhc.xsZWvb.ecRggb,#rhs .Wnoohf .xpdopen .wDYxhc.EfDVh.ecRggb,#rhs .dG2XIf .ecRggb{padding-bottom:15px}.ecRggb{background-color:#fff;box-shadow:none;border:1px solid #dadce0;border-radius:8px;margin:0 0 16px 0}.tWSgNb .cAn2Qb{border-bottom:none}.Jb0Zif .UiGGAb.ILfuVd,.ILfuVd{font-size:16px;line-height:24px;}.fm06If .ILfuVd.NA6bn,.c2xzTb .ILfuVd.duSGDe,.c2xzTb .ILfuVd.NA6bn.c3biWd{font-size:14px;line-height:1.58;}.c2xzTb .zloOqf{font-size:16px;margin-bottom:16px;margin-top:-8px;}.FLWspc{margin:16px}.LFYdN{font-size:16px;margin:16px}.trNcde .ILfuVd{color:var(–bbQxAb);font-family:Google Sans,arial,sans-serif;font-size:14px;line-height:22px}.HSryR .ILfuVd{line-height:1.5}.ss6qqb .ILfuVd,.ss6qqb .UiGGAb.ILfuVd{font-size:14px;line-height:22px}.c2xzTb .qLYAZd{margin:16px 16px 16px 0;}.d9FyLd{padding:0 0 10px}.hgKElc{padding:0 8px 0 0}.kX21rb{font-size:12px;line-height:1.34;display:inline-block;font-family:Google Sans,arial,sans-serif;padding-right:0;white-space:nowrap}.SPV4pd{display:flex;overflow-x:auto}.SPV4pd::-webkit-scrollbar{display:none}.Vjskue{margin-left:8px}.JT9o0,.ZnIJV{align-items:center;border:1px solid var(–mXZkqc);border-radius:16px;box-sizing:border-box;color:#1a73e8;cursor:pointer;display:flex;height:32px;margin-bottom:16px}.BkHX0d{font-family:Google Sans,arial,sans-serif-medium,sans-serif;font-size:14px;line-height:20px;padding-right:20px;text-align:center;white-space:nowrap}.xv1D5b{display:block;padding:0 8px 0 12px;width:18px;height:18px}.LGOjhe{overflow:hidden;padding-bottom:20px}.trNcde .LGOjhe{overflow:visible}.SALvLe .LGOjhe,.Jb0Zif .LGOjhe,.HSryR .LGOjhe,.IVvPP .LGOjhe{padding:0 0 10px;margin:10px 0 0 0}.s6JM6d .SALvLe .LGOjhe{margin-top:12px;}.s6JM6d .HSryR .LGOjhe{margin-top:12px;padding-bottom:20px}#res .Jb0Zif .qDOt0b h3,.IVvPP .qDOt0b h3{font-size:16px;line-height:1.375}.Jb0Zif .qDOt0b .iUh30,.IVvPP .qDOt0b .iUh30{font-size:14px;line-height:1.58}.IVvPP .qDOt0b{border-bottom:1px solid var(–gS5jXb);padding-bottom:6px}.rjOVwe.ILfuVd{font-size:16px;line-height:20px}.dG2XIf .rjOVwe{padding-top:22px;padding-bottom:0;margin-bottom:1px}.xWd7I{padding-top:12px;}.ILfuVd.NA6bn,.ILfuVd.duSGDe,.ILfuVd.UiGGAb,.IVvPP .ILfuVd{font-size:14px;line-height:22px}.n6SJS .ILfuVd{font-size:14px}.ILfuVd.NA6bn,.ILfuVd.duSGDe,.ILfuVd.UiGGAb,.IVvPP .ILfuVd{line-height:20px}.xpd-wa .g-blk{margin:initial}.xpd-wa .dG2XIf{border:initial;box-shadow:none}.fm06If .ILfuVd,.c2xzTb .ILfuVd,.Jb0Zif .c2xzTb .ILfuVd{font-family:Google Sans,arial,sans-serif;color:var(–YLNNHc)}.fm06If .ILfuVd,.c2xzTb .ILfuVd,.Jb0Zif .c2xzTb .ILfuVd{font-size:20px;line-height:28px}.cUnQKe .ILfuVd,.cUnQKe .UiGGAb.ILfuVd,.w5mTAe .ILfuVd,.W0urI .ILfuVd{color:var(–bbQxAb);font-family:Google Sans,arial,sans-serif;font-size:16px;line-height:24px}.fm06If .ILfuVd b,.trNcde .ILfuVd b,.cUnQKe .ILfuVd b,.c2xzTb .ILfuVd b,.w5mTAe .ILfuVd b,.W0urI .ILfuVd b{background-color:#d3e3fd;color:#040c28;font-weight:500}@media (forced-colors:active){.fm06If .ILfuVd b,.c2xzTb .ILfuVd b,.trNcde .ILfuVd b,.cUnQKe .ILfuVd b,.w5mTAe .ILfuVd b,.W0urI .ILfuVd b{background-color:Mark;color:MarkText}}.vBnbff .mO5MMe{padding-top:10px}.cUnQKe .vBnbff .mO5MMe{padding-left:0;}.trNcde .vBnbff .mO5MMe{padding:10px 0 0 0}.cAn2Qb.abzPbc .mnr-c{max-width:calc(100% – 162px)}.tF2Cxc{position:relative}.Jb0Zif .BDNLRc{margin:16px 16px -11px}.RUXr2d{display:inline}.MTB56{margin-right:12px;vertical-align:middle}.Pthbuf{display:flex;align-items:center}.m164Nd{vertical-align:middle;display:inline-block}.qpGQpf{clear:both;padding-top:6px}.aCOpRe{line-height:1.58;word-wrap:break-word}.aCOpRe sup{line-height:0.9}.yuRUbf{font-weight:normal;font-size:small;line-height:1.58;}.IsZvec{max-width:48em;color:#4d5156;line-height:1.58}.uo4vr{color:var(–IXoxUe);line-height:1.58}.IjZ7ze{display:inline-block;color:var(–IXoxUe);font-size:12px;line-height:1.34;white-space:nowrap}.FyYA1e{margin:5px 0}a:hover h3.LC20lb{text-decoration:underline}.M8OgIe .dG2XIf .fm06If .LC20lb,.n6SJS h3.LC20lb{overflow:hidden;text-overflow:ellipsis;white-space:nowrap;width:100%}.LC20lb{display:inline-block;line-height:1.3;margin-bottom:3px;}.c2xzTb .LC20lb{margin-bottom:0}.MMgsKf{padding-top:2px}.DKV0Md{padding-top:4px;padding-top:5px;}.Z3xoIb{padding-top:27px;padding-top:28px;}.NXKJM{display:-webkit-box;overflow:hidden;-webkit-box-orient:vertical;-webkit-line-clamp:1}.hceuRc{-webkit-box-orient:vertical;display:-webkit-box;-webkit-line-clamp:2;overflow:hidden}.fzBvHb{font-weight:700}.DKV0Md,.Z3xoIb{margin-top:18px;}.xvfwl{margin-top:4px}.q0vns a.fl{font-size:12px}.TQc1id .qLRx3b{font-size:14px;line-height:1.58}.HGLrXd{display:inline-block;-webkit-text-size-adjust:none}.q0vns{display:inline-block;padding-bottom:2px;padding-top:1px}.NJjxre{position:absolute;left:0;top:0;width:100%}.M8OgIe .VWCdhc.Mjve0e .q0vns{width:max-content}.VjDLd .TieM1d .tjvcx,.IVvPP .tjvcx,.kno-kp .tjvcx,.VjDLd .kp-wholepage-osrp .tjvcx,#rhs .ss6qqb .tjvcx,#rhs .trNcde .tjvcx{display:inline-block;height:19px;overflow-y:hidden}.ojE3Fb{padding:0;padding-bottom:0;}.ojE3Fb .q0vns{display:flex;overflow:hidden;padding:0;padding-bottom:0;align-items:center;}.ojE3Fb .q0vns a.fl{padding-top:0;font-size:12px;line-height:18px;}.GvPZzd{font-size:12px;line-height:18px;}.dTxz9{padding-right:38px}.iG7WGe{color:#202124;padding:0;text-align:center;width:16px}.VuuXrf{color:#202124;font-size:14px;display:block;line-height:20px;white-space:nowrap;}.qncq2c{font-size:12px;line-height:16px;margin-left:6px}.CA5RN{overflow:hidden}.K2VDSb{display:flex;flex-direction:row}.H9lube{background-color:#f1f3f4;border:1px solid #dadce0;border-radius:50%;display:inline-flex;justify-content:center;align-items:center;height:26px;width:26px;margin-right:12px;flex-shrink:0;vertical-align:middle;}.fJOpI.H9lube{background-color:#e2eeff;border:1px solid #e2eeff}.P1UpZb{background-color:#f1f3f4;border:1px solid #ecedef}.eqA2re.NjwKYd{margin-right:0}.Vwoesf:not(.oRVWZ){display:inline-block}.Vwoesf{vertical-align:middle}.XNo5Ab.XNo5Ab{display:block;}.lWlVCe{border-radius:50%}.bJVp8c{color:#0060f0}.Jj3Uob{color:#0060f0;}.ob9lvb{color:#4d5156}.ob9lvb.HCMUuf{color:var(–IXoxUe)}.ylgVCe{color:#4d5156}.B6fmyf{position:absolute;top:0;height:0;visibility:hidden;white-space:nowrap;width:100%}.B6fmyf.Mg1HEd{height:auto}.ljeAnf{display:-webkit-box;overflow:hidden;-webkit-box-orient:vertical}
Regular expressions are particularly useful for defining filters. Regular expressions contain a series of characters that define a pattern of text to be matched—to make a filter more specialized, or general. For example, the regular expression ^AL[.]* searches for all items beginning with AL.

Why do people use regular expressions

.wDYxhc{clear:both}.cUnQKe .wDYxhc,.related-question-pair .wDYxhc,.M8OgIe .fm06If .wDYxhc{clear:none}html .dG2XIf .xpdclose .LKPcQc,html .dG2XIf .xpdopen .viOShc{padding-top:0;}.garHBe{color:var(–COEmY);font-size:20px;line-height:1.3;position:relative}.garHBe a{color:var(–COEmY)}.xpdopen .Hhmu2e{overflow:inherit}.xpdclose .a84NUc:not(:empty),.xpdopen .CQKTwc:not(:empty){border-top:solid 1px #ebebeb;border-radius:0}.xpdclose .pmYXee .a84NUc:not(:empty),.xpdopen .pmYXee .CQKTwc:not(:empty){border-top:none}.cAn2Qb .a84NUc:not(:empty),.cAn2Qb .CQKTwc:not(:empty){border-top:none}.SHa8ve{display:none}.xpdclose .TOfaBb.SHa8ve,.xpdopen .LL5J7d.SHa8ve{display:block}.rKR6H{padding-top:0.1px}.xpdclose .oHglmf,.xpdopen .xzPb7d{padding-bottom:16px}.xpdclose .kp-header .oHglmf,.xpdopen .kp-header .xzPb7d{padding-bottom:0}.c2xzTb .xpdclose .oHglmf,.c2xzTb .xpdopen .xzPb7d{padding-bottom:0}.HSryR .xpdclose .oHglmf,.HSryR .xpdopen .xzPb7d{padding-bottom:0}.Wnoohf .xpdopen .yp1CPe,.OJXvsb .xpdclose .siXlze{padding-bottom:16px}.Wnoohf .xpdopen .yp1CPe .xpdbox g-more-link{top:28px}.Wnoohf .xpdclose .wDYxhc.xsZWvb,.Wnoohf .xpdopen .wDYxhc.EfDVh{padding-bottom:0}.OJXvsb .xpdclose .wDYxhc.siXlze{padding-bottom:16px}#rhs .dG2XIf .xpdclose .LKPcQc,#rhs .dG2XIf .xpdopen .viOShc{padding-top:0}#rhs .Wnoohf .xpdopen .yp1CPe,#rhs .OJXvsb .xpdclose .siXlze{padding-bottom:15px}#rhs .Wnoohf .xpdclose .wDYxhc.xsZWvb,#rhs .Wnoohf .xpdopen .wDYxhc.EfDVh{padding-bottom:0}#rhs .Wnoohf .xpdclose .wDYxhc.xsZWvb.ecRggb,#rhs .Wnoohf .xpdopen .wDYxhc.EfDVh.ecRggb,#rhs .dG2XIf .ecRggb{padding-bottom:15px}.ecRggb{background-color:#fff;box-shadow:none;border:1px solid #dadce0;border-radius:8px;margin:0 0 16px 0}.tWSgNb .cAn2Qb{border-bottom:none}.IiOSLb .rsGxI.Ww4FFb,.Ww4FFb{background-color:var(–xhUGwc);border-radius:0px;border-width:0;box-shadow:none}.Ww4FFb .mnr-c:not(:empty),.mnr-c:not(:empty) .Ww4FFb,.Ww4FFb .Ww4FFb{box-shadow:none;margin-bottom:0px}.vt6azd{margin:0px 0px 8px}.vt6azd{margin:0px 0px 30px}.CBvvz{margin:-var(–sds-sys-measurement–space-sm) 0px 0px}.CBvvz{margin:-30px 0px 0px}.Jb0Zif .UiGGAb.ILfuVd,.ILfuVd{font-size:16px;line-height:24px;}.fm06If .ILfuVd.NA6bn,.c2xzTb .ILfuVd.duSGDe,.c2xzTb .ILfuVd.NA6bn.c3biWd{font-size:14px;line-height:1.58;}.c2xzTb .zloOqf{font-size:16px;margin-bottom:16px;margin-top:-8px;}.FLWspc{margin:16px}.LFYdN{font-size:16px;margin:16px}.trNcde .ILfuVd{color:var(–bbQxAb);font-family:Google Sans,arial,sans-serif;font-size:14px;line-height:22px}.HSryR .ILfuVd{line-height:1.5}.ss6qqb .ILfuVd,.ss6qqb .UiGGAb.ILfuVd{font-size:14px;line-height:22px}.c2xzTb .qLYAZd{margin:16px 16px 16px 0;}.d9FyLd{padding:0 0 10px}.hgKElc{padding:0 8px 0 0}.kX21rb{font-size:12px;line-height:1.34;display:inline-block;font-family:Google Sans,arial,sans-serif;padding-right:0;white-space:nowrap}.SPV4pd{display:flex;overflow-x:auto}.SPV4pd::-webkit-scrollbar{display:none}.Vjskue{margin-left:8px}.JT9o0,.ZnIJV{align-items:center;border:1px solid var(–mXZkqc);border-radius:16px;box-sizing:border-box;color:#1a73e8;cursor:pointer;display:flex;height:32px;margin-bottom:16px}.BkHX0d{font-family:Google Sans,arial,sans-serif-medium,sans-serif;font-size:14px;line-height:20px;padding-right:20px;text-align:center;white-space:nowrap}.xv1D5b{display:block;padding:0 8px 0 12px;width:18px;height:18px}.LGOjhe{overflow:hidden;padding-bottom:20px}.trNcde .LGOjhe{overflow:visible}.SALvLe .LGOjhe,.Jb0Zif .LGOjhe,.HSryR .LGOjhe,.IVvPP .LGOjhe{padding:0 0 10px;margin:10px 0 0 0}.s6JM6d .SALvLe .LGOjhe{margin-top:12px;}.s6JM6d .HSryR .LGOjhe{margin-top:12px;padding-bottom:20px}#res .Jb0Zif .qDOt0b h3,.IVvPP .qDOt0b h3{font-size:16px;line-height:1.375}.Jb0Zif .qDOt0b .iUh30,.IVvPP .qDOt0b .iUh30{font-size:14px;line-height:1.58}.IVvPP .qDOt0b{border-bottom:1px solid var(–gS5jXb);padding-bottom:6px}.rjOVwe.ILfuVd{font-size:16px;line-height:20px}.dG2XIf .rjOVwe{padding-top:22px;padding-bottom:0;margin-bottom:1px}.xWd7I{padding-top:12px;}.ILfuVd.NA6bn,.ILfuVd.duSGDe,.ILfuVd.UiGGAb,.IVvPP .ILfuVd{font-size:14px;line-height:22px}.n6SJS .ILfuVd{font-size:14px}.ILfuVd.NA6bn,.ILfuVd.duSGDe,.ILfuVd.UiGGAb,.IVvPP .ILfuVd{line-height:20px}.xpd-wa .g-blk{margin:initial}.xpd-wa .dG2XIf{border:initial;box-shadow:none}.fm06If .ILfuVd,.c2xzTb .ILfuVd,.Jb0Zif .c2xzTb .ILfuVd{font-family:Google Sans,arial,sans-serif;color:var(–YLNNHc)}.fm06If .ILfuVd,.c2xzTb .ILfuVd,.Jb0Zif .c2xzTb .ILfuVd{font-size:20px;line-height:28px}.cUnQKe .ILfuVd,.cUnQKe .UiGGAb.ILfuVd,.w5mTAe .ILfuVd,.W0urI .ILfuVd{color:var(–bbQxAb);font-family:Google Sans,arial,sans-serif;font-size:16px;line-height:24px}.fm06If .ILfuVd b,.trNcde .ILfuVd b,.cUnQKe .ILfuVd b,.c2xzTb .ILfuVd b,.w5mTAe .ILfuVd b,.W0urI .ILfuVd b{background-color:#d3e3fd;color:#040c28;font-weight:500}@media (forced-colors:active){.fm06If .ILfuVd b,.c2xzTb .ILfuVd b,.trNcde .ILfuVd b,.cUnQKe .ILfuVd b,.w5mTAe .ILfuVd b,.W0urI .ILfuVd b{background-color:Mark;color:MarkText}}.vBnbff .mO5MMe{padding-top:10px}.cUnQKe .vBnbff .mO5MMe{padding-left:0;}.trNcde .vBnbff .mO5MMe{padding:10px 0 0 0}.cAn2Qb.abzPbc .mnr-c{max-width:calc(100% – 162px)}.tF2Cxc{position:relative}.Jb0Zif .BDNLRc{margin:16px 16px -11px}.RUXr2d{display:inline}.MTB56{margin-right:12px;vertical-align:middle}.Pthbuf{display:flex;align-items:center}.m164Nd{vertical-align:middle;display:inline-block}.qpGQpf{clear:both;padding-top:6px}.aCOpRe{line-height:1.58;word-wrap:break-word}.aCOpRe sup{line-height:0.9}.yuRUbf{font-weight:normal;font-size:small;line-height:1.58;}.IsZvec{max-width:48em;color:#4d5156;line-height:1.58}.uo4vr{color:var(–IXoxUe);line-height:1.58}.IjZ7ze{display:inline-block;color:var(–IXoxUe);font-size:12px;line-height:1.34;white-space:nowrap}.FyYA1e{margin:5px 0}a:hover h3.LC20lb{text-decoration:underline}.M8OgIe .dG2XIf .fm06If .LC20lb,.n6SJS h3.LC20lb{overflow:hidden;text-overflow:ellipsis;white-space:nowrap;width:100%}.LC20lb{display:inline-block;line-height:1.3;margin-bottom:3px;}.c2xzTb .LC20lb{margin-bottom:0}.MMgsKf{padding-top:2px}.DKV0Md{padding-top:4px;padding-top:5px;}.Z3xoIb{padding-top:27px;padding-top:28px;}.NXKJM{display:-webkit-box;overflow:hidden;-webkit-box-orient:vertical;-webkit-line-clamp:1}.hceuRc{-webkit-box-orient:vertical;display:-webkit-box;-webkit-line-clamp:2;overflow:hidden}.fzBvHb{font-weight:700}.DKV0Md,.Z3xoIb{margin-top:18px;}.xvfwl{margin-top:4px}.q0vns a.fl{font-size:12px}.TQc1id .qLRx3b{font-size:14px;line-height:1.58}.HGLrXd{display:inline-block;-webkit-text-size-adjust:none}.q0vns{display:inline-block;padding-bottom:2px;padding-top:1px}.NJjxre{position:absolute;left:0;top:0;width:100%}.M8OgIe .VWCdhc.Mjve0e .q0vns{width:max-content}.VjDLd .TieM1d .tjvcx,.IVvPP .tjvcx,.kno-kp .tjvcx,.VjDLd .kp-wholepage-osrp .tjvcx,#rhs .ss6qqb .tjvcx,#rhs .trNcde .tjvcx{display:inline-block;height:19px;overflow-y:hidden}.ojE3Fb{padding:0;padding-bottom:0;}.ojE3Fb .q0vns{display:flex;overflow:hidden;padding:0;padding-bottom:0;align-items:center;}.ojE3Fb .q0vns a.fl{padding-top:0;font-size:12px;line-height:18px;}.GvPZzd{font-size:12px;line-height:18px;}.dTxz9{padding-right:38px}.iG7WGe{color:#202124;padding:0;text-align:center;width:16px}.VuuXrf{color:#202124;font-size:14px;display:block;line-height:20px;white-space:nowrap;}.qncq2c{font-size:12px;line-height:16px;margin-left:6px}.CA5RN{overflow:hidden}.K2VDSb{display:flex;flex-direction:row}.H9lube{background-color:#f1f3f4;border:1px solid #dadce0;border-radius:50%;display:inline-flex;justify-content:center;align-items:center;height:26px;width:26px;margin-right:12px;flex-shrink:0;vertical-align:middle;}.fJOpI.H9lube{background-color:#e2eeff;border:1px solid #e2eeff}.P1UpZb{background-color:#f1f3f4;border:1px solid #ecedef}.eqA2re.NjwKYd{margin-right:0}.Vwoesf:not(.oRVWZ){display:inline-block}.Vwoesf{vertical-align:middle}.XNo5Ab.XNo5Ab{display:block;}.lWlVCe{border-radius:50%}.b
JVp8c{color:#0060f0}.Jj3Uob{color:#0060f0;}.ob9lvb{color:#4d5156}.ob9lvb.HCMUuf{color:var(–IXoxUe)}.ylgVCe{color:#4d5156}.B6fmyf{position:absolute;top:0;height:0;visibility:hidden;white-space:nowrap;width:100%}.B6fmyf.Mg1HEd{height:auto}.ljeAnf{display:-webkit-box;overflow:hidden;-webkit-box-orient:vertical}.byrV5b{align-items:center;display:flex;flex-direction:row}.sBJG1d{display:flex;flex-direction:row;justify-content:center}.kDmHO{align-items:center;display:flex;flex-direction:column}.lR4vec{display:flex;flex-direction:column;justify-content:center}.xTEyc{align-items:start;display:flex;flex-direction:row}.OjFzvd{display:flex;flex-direction:row;justify-content:start}.YIPhrb{align-items:start;display:flex;flex-direction:column}.BToiNc{display:flex;flex-direction:column;justify-content:start}.E4bmEc .Va021{flex:1 1 100%}.E4bmEc .Y76LGf{flex:1 1 calc(50% – 4px)}
Regular expressions are particularly useful for defining filters. Regular expressions contain a series of characters that define a pattern of text to be matched—to make a filter more specialized, or general. For example, the regular expression ^AL[.]*

.wDYxhc{clear:both}.cUnQKe .wDYxhc,.related-question-pair .wDYxhc,.M8OgIe .fm06If .wDYxhc{clear:none}html .dG2XIf .xpdclose .LKPcQc,html .dG2XIf .xpdopen .viOShc{padding-top:0;}.garHBe{color:var(–COEmY);font-size:20px;line-height:1.3;position:relative}.garHBe a{color:var(–COEmY)}.xpdopen .Hhmu2e{overflow:inherit}.xpdclose .a84NUc:not(:empty),.xpdopen .CQKTwc:not(:empty){border-top:solid 1px #ebebeb;border-radius:0}.xpdclose .pmYXee .a84NUc:not(:empty),.xpdopen .pmYXee .CQKTwc:not(:empty){border-top:none}.cAn2Qb .a84NUc:not(:empty),.cAn2Qb .CQKTwc:not(:empty){border-top:none}.SHa8ve{display:none}.xpdclose .TOfaBb.SHa8ve,.xpdopen .LL5J7d.SHa8ve{display:block}.rKR6H{padding-top:0.1px}.xpdclose .oHglmf,.xpdopen .xzPb7d{padding-bottom:16px}.xpdclose .kp-header .oHglmf,.xpdopen .kp-header .xzPb7d{padding-bottom:0}.c2xzTb .xpdclose .oHglmf,.c2xzTb .xpdopen .xzPb7d{padding-bottom:0}.HSryR .xpdclose .oHglmf,.HSryR .xpdopen .xzPb7d{padding-bottom:0}.Wnoohf .xpdopen .yp1CPe,.OJXvsb .xpdclose .siXlze{padding-bottom:16px}.Wnoohf .xpdopen .yp1CPe .xpdbox g-more-link{top:28px}.Wnoohf .xpdclose .wDYxhc.xsZWvb,.Wnoohf .xpdopen .wDYxhc.EfDVh{padding-bottom:0}.OJXvsb .xpdclose .wDYxhc.siXlze{padding-bottom:16px}#rhs .dG2XIf .xpdclose .LKPcQc,#rhs .dG2XIf .xpdopen .viOShc{padding-top:0}#rhs .Wnoohf .xpdopen .yp1CPe,#rhs .OJXvsb .xpdclose .siXlze{padding-bottom:15px}#rhs .Wnoohf .xpdclose .wDYxhc.xsZWvb,#rhs .Wnoohf .xpdopen .wDYxhc.EfDVh{padding-bottom:0}#rhs .Wnoohf .xpdclose .wDYxhc.xsZWvb.ecRggb,#rhs .Wnoohf .xpdopen .wDYxhc.EfDVh.ecRggb,#rhs .dG2XIf .ecRggb{padding-bottom:15px}.ecRggb{background-color:#fff;box-shadow:none;border:1px solid #dadce0;border-radius:8px;margin:0 0 16px 0}.tWSgNb .cAn2Qb{border-bottom:none}.Jb0Zif .UiGGAb.ILfuVd,.ILfuVd{font-size:16px;line-height:24px;}.fm06If .ILfuVd.NA6bn,.c2xzTb .ILfuVd.duSGDe,.c2xzTb .ILfuVd.NA6bn.c3biWd{font-size:14px;line-height:1.58;}.c2xzTb .zloOqf{font-size:16px;margin-bottom:16px;margin-top:-8px;}.FLWspc{margin:16px}.LFYdN{font-size:16px;margin:16px}.trNcde .ILfuVd{color:var(–bbQxAb);font-family:Google Sans,arial,sans-serif;font-size:14px;line-height:22px}.HSryR .ILfuVd{line-height:1.5}.ss6qqb .ILfuVd,.ss6qqb .UiGGAb.ILfuVd{font-size:14px;line-height:22px}.c2xzTb .qLYAZd{margin:16px 16px 16px 0;}.d9FyLd{padding:0 0 10px}.hgKElc{padding:0 8px 0 0}.kX21rb{font-size:12px;line-height:1.34;display:inline-block;font-family:Google Sans,arial,sans-serif;padding-right:0;white-space:nowrap}.SPV4pd{display:flex;overflow-x:auto}.SPV4pd::-webkit-scrollbar{display:none}.Vjskue{margin-left:8px}.JT9o0,.ZnIJV{align-items:center;border:1px solid var(–mXZkqc);border-radius:16px;box-sizing:border-box;color:#1a73e8;cursor:pointer;display:flex;height:32px;margin-bottom:16px}.BkHX0d{font-family:Google Sans,arial,sans-serif-medium,sans-serif;font-size:14px;line-height:20px;padding-right:20px;text-align:center;white-space:nowrap}.xv1D5b{display:block;padding:0 8px 0 12px;width:18px;height:18px}.LGOjhe{overflow:hidden;padding-bottom:20px}.trNcde .LGOjhe{overflow:visible}.SALvLe .LGOjhe,.Jb0Zif .LGOjhe,.HSryR .LGOjhe,.IVvPP .LGOjhe{padding:0 0 10px;margin:10px 0 0 0}.s6JM6d .SALvLe .LGOjhe{margin-top:12px;}.s6JM6d .HSryR .LGOjhe{margin-top:12px;padding-bottom:20px}#res .Jb0Zif .qDOt0b h3,.IVvPP .qDOt0b h3{font-size:16px;line-height:1.375}.Jb0Zif .qDOt0b .iUh30,.IVvPP .qDOt0b .iUh30{font-size:14px;line-height:1.58}.IVvPP .qDOt0b{border-bottom:1px solid var(–gS5jXb);padding-bottom:6px}.rjOVwe.ILfuVd{font-size:16px;line-height:20px}.dG2XIf .rjOVwe{padding-top:22px;padding-bottom:0;margin-bottom:1px}.xWd7I{padding-top:12px;}.ILfuVd.NA6bn,.ILfuVd.duSGDe,.ILfuVd.UiGGAb,.IVvPP .ILfuVd{font-size:14px;line-height:22px}.n6SJS .ILfuVd{font-size:14px}.ILfuVd.NA6bn,.ILfuVd.duSGDe,.ILfuVd.UiGGAb,.IVvPP .ILfuVd{line-height:20px}.xpd-wa .g-blk{margin:initial}.xpd-wa .dG2XIf{border:initial;box-shadow:none}.fm06If .ILfuVd,.c2xzTb .ILfuVd,.Jb0Zif .c2xzTb .ILfuVd{font-family:Google Sans,arial,sans-serif;color:var(–YLNNHc)}.fm06If .ILfuVd,.c2xzTb .ILfuVd,.Jb0Zif .c2xzTb .ILfuVd{font-size:20px;line-height:28px}.cUnQKe .ILfuVd,.cUnQKe .UiGGAb.ILfuVd,.w5mTAe .ILfuVd,.W0urI .ILfuVd{color:var(–bbQxAb);font-family:Google Sans,arial,sans-serif;font-size:16px;line-height:24px}.fm06If .ILfuVd b,.trNcde .ILfuVd b,.cUnQKe .ILfuVd b,.c2xzTb .ILfuVd b,.w5mTAe .ILfuVd b,.W0urI .ILfuVd b{background-color:#d3e3fd;color:#040c28;font-weight:500}@media (forced-colors:active){.fm06If .ILfuVd b,.c2xzTb .ILfuVd b,.trNcde .ILfuVd b,.cUnQKe .ILfuVd b,.w5mTAe .ILfuVd b,.W0urI .ILfuVd b{background-color:Mark;color:MarkText}}.vBnbff .mO5MMe{padding-top:10px}.cUnQKe .vBnbff .mO5MMe{padding-left:0;}.trNcde .vBnbff .mO5MMe{padding:10px 0 0 0}.cAn2Qb.abzPbc .mnr-c{max-width:calc(100% – 162px)}.tF2Cxc{position:relative}.Jb0Zif .BDNLRc{margin:16px 16px -11px}.RUXr2d{display:inline}.MTB56{margin-right:12px;vertical-align:middle}.Pthbuf{display:flex;align-items:center}.m164Nd{vertical-align:middle;display:inline-block}.qpGQpf{clear:both;padding-top:6px}.aCOpRe{line-height:1.58;word-wrap:break-word}.aCOpRe sup{line-height:0.9}.yuRUbf{font-weight:normal;font-size:small;line-height:1.58;}.IsZvec{max-width:48em;color:#4d5156;line-height:1.58}.uo4vr{color:var(–IXoxUe);line-height:1.58}.IjZ7ze{display:inline-block;color:var(–IXoxUe);font-size:12px;line-height:1.34;white-space:nowrap}.FyYA1e{margin:5px 0}a:hover h3.LC20lb{text-decoration:underline}.M8OgIe .dG2XIf .fm06If .LC20lb,.n6SJS h3.LC20lb{overflow:hidden;text-overflow:ellipsis;white-space:nowrap;width:100%}.LC20lb{display:inline-block;line-height:1.3;margin-bottom:3px;}.c2xzTb .LC20lb{margin-bottom:0}.MMgsKf{padding-top:2px}.DKV0Md{padding-top:4px;padding-top:5px;}.Z3xoIb{padding-top:27px;padding-top:28px;}.NXKJM{display:-webkit-box;overflow:hidden;-webkit-box-orient:vertical;-webkit-line-clamp:1}.hceuRc{-webkit-box-orient:vertical;display:-webkit-box;-webkit-line-clamp:2;overflow:hidden}.fzBvHb{font-weight:700}.DKV0Md,.Z3xoIb{margin-top:18px;}.xvfwl{margin-top:4px}.q0vns a.fl{font-size:12px}.TQc1id .qLRx3b{font-size:14px;line-height:1.58}.HGLrXd{display:inline-block;-webkit-text-size-adjust:none}.q0vns{display:inline-block;padding-bottom:2px;padding-top:1px}.NJjxre{position:absolute;left:0;top:0;width:100%}.M8OgIe .VWCdhc.Mjve0e .q0vns{width:max-content}.VjDLd .TieM1d .tjvcx,.IVvPP .tjvcx,.kno-kp .tjvcx,.VjDLd .kp-wholepage-osrp .tjvcx,#rhs .ss6qqb .tjvcx,#rhs .trNcde .tjvcx{display:inline-block;height:19px;overflow-y:hidden}.ojE3Fb{padding:0;padding-bottom:0;}.ojE3Fb .q0vns{display:flex;overflow:hidden;padding:0;padding-bottom:0;align-items:center;}.ojE3Fb .q0vns a.fl{padding-top:0;font-size:12px;line-height:18px;}.GvPZzd{font-size:12px;line-height:18px;}.dTxz9{padding-right:38px}.iG7WGe{color:#202124;padding:0;text-align:center;width:16px}.VuuXrf{color:#202124;font-size:14px;display:block;line-height:20px;white-space:nowrap;}.qncq2c{font-size:12px;line-height:16px;margin-left:6px}.CA5RN{overflow:hidden}.K2VDSb{display:flex;flex-direction:row}.H9lube{background-color:#f1f3f4;border:1px solid #dadce0;border-radius:50%;display:inline-flex;justify-content:center;align-items:center;height:26px;width:26px;margin-right:12px;flex-shrink:0;vertical-align:middle;}.fJOpI.H9lube{background-color:#e2eeff;border:1px solid #e2eeff}.P1UpZb{background-color:#f1f3f4;border:1px solid #ecedef}.eqA2re.NjwKYd{margin-right:0}.Vwoesf:not(.oRVWZ){display:inline-block}.Vwoesf{vertical-align:middle}.XNo5Ab.XNo5Ab{display:block;}.lWlVCe{border-radius:50%}.bJVp8c{color:#0060f0}.Jj3Uob{color:#0060f0;}.ob9lvb{color:#4d5156}.ob9lvb.HCMUuf{color:var(–IXoxUe)}.ylgVCe{color:#4d5156}.B6fmyf{position:absolute;top:0;height:0;visibility:hidden;white-space:nowrap;width:100%}.B6fmyf.Mg1HEd{height:auto}.ljeAnf{display:-webkit-box;overflow:hidden;-webkit-box-orient:vertical}
Using regex can make locating information much easier. Once you find your target, you can batch edit/replate/delete or whatever processing you need to do. Some practical examples of using regex are batch file renaming, parsing logs, validating forms, making mass edits in a codebase, and recursive search..wDYxhc{clear:both}.cUnQKe .wDYxhc,.related-question-pair .wDYxhc,.M8OgIe .fm06If .wDYxhc{clear:none}html .dG2XIf .xpdclose .LKPcQc,html .dG2XIf .xpdopen .viOShc{padding-top:0;}.garHBe{color:var(–COEmY);font-size:20px;line-height:1.3;position:relative}.garHBe a{color:var(–COEmY)}.xpdopen .Hhmu2e{overflow:inherit}.xpdclose .a84NUc:not(:empty),.xpdopen .CQKTwc:not(:empty){border-top:solid 1px #ebebeb;border-radius:0}.xpdclose .pmYXee .a84NUc:not(:empty),.xpdopen .pmYXee .CQKTwc:not(:empty){border-top:none}.cAn2Qb .a84NUc:not(:empty),.cAn2Qb .CQKTwc:not(:empty){border-top:none}.SHa8ve{display:none}.xpdclose .TOfaBb.SHa8ve,.xpdopen .LL5J7d.SHa8ve{display:block}.rKR6H{padding-top:0.1px}.xpdclose .oHglmf,.xpdopen .xzPb7d{padding-bottom:16px}.xpdclose .kp-header .oHglmf,.xpdopen .kp-header .xzPb7d{padding-bottom:0}.c2xzTb .xpdclose .oHglmf,.c2xzTb .xpdopen .xzPb7d{padding-bottom:0}.HSryR .xpdclose .oHglmf,.HSryR .xpdopen .xzPb7d{padding-bottom:0}.Wnoohf .xpdopen .yp1CPe,.OJXvsb .xpdclose .siXlze{padding-bottom:16px}.Wnoohf .xpdopen .yp1CPe .xpdbox g-more-link{top:28px}.Wnoohf .xpdclose .wDYxhc.xsZWvb,.Wnoohf .xpdopen .wDYxhc.EfDVh{padding-bottom:0}.OJXvsb .xpdclose .wDYxhc.siXlze{padding-bottom:16px}#rhs .dG2XIf .xpdclose .LKPcQc,#rhs .dG2XIf .xpdopen .viOShc{padding-top:0}#rhs .Wnoohf .xpdopen .yp1CPe,#rhs .OJXvsb .xpdclose .siXlze{padding-bottom:15px}#rhs .Wnoohf .xpdclose .wDYxhc.xsZWvb,#rhs .Wnoohf .xpdopen .wDYxhc.EfDVh{padding-bottom:0}#rhs .Wnoohf .xpdclose .wDYxhc.xsZWvb.ecRggb,#rhs .Wnoohf .xpdopen .wDYxhc.EfDVh.ecRggb,#rhs .dG2XIf .ecRggb{padding-bottom:15px}.ecRggb{background-color:#fff;box-shadow:none;border:1px solid #dadce0;border-radius:8px;margin:0 0 16px 0}.tWSgNb .cAn2Qb{border-bottom:none}.IiOSLb .rsGxI.Ww4FFb,.Ww4FFb{background-color:var(–xhUGwc);border-radius:0px;border-width:0;box-shadow:none}.Ww4FFb .mnr-c:not(:empty),.mnr-c:not(:empty) .Ww4FFb,.Ww4FFb .Ww4FFb{box-shadow:none;margin-bottom:0px}.vt6azd{margin:0px 0px 8px}.vt6azd{margin:0px 0px 30px}.CBvvz{margin:-var(–sds-sys-measurement–space-sm) 0px 0px}.CBvvz{margin:-30px 0px 0px}.Jb0Zif .UiGGAb.ILfuVd,.ILfuVd{font-size:16px;line-height:24px;}.fm06If .ILfuVd.NA6bn,.c2xzTb .ILfuVd.duSGDe,.c2xzTb .ILfuVd.NA6bn.c3biWd{font-size:14px;line-height:1.58;}.c2xzTb .zloOqf{font-size:16px;margin-bottom:16px;margin-top:-8px;}.FLWspc{margin:16px}.LFYdN{font-size:16px;margin:16px}.trNcde .ILfuVd{color:var(–bbQxAb);font-family:Google Sans,arial,sans-serif;font-size:14px;line-height:22px}.HSryR .ILfuVd{line-height:1.5}.ss6qqb .ILfuVd,.ss6qqb .UiGGAb.ILfuVd{font-size:14px;line-height:22px}.c2xzTb .qLYAZd{margin:16px 16px 16px 0;}.d9FyLd{padding:0 0 10px}.hgKElc{padding:0 8px 0 0}.kX21rb{font-size:12px;line-height:1.34;display:inline-block;font-family:Google Sans,arial,sans-serif;padding-right:0;white-space:nowrap}.SPV4pd{display:flex;overflow-x:auto}.SPV4pd::-webkit-scrollbar{display:none}.Vjskue{margin-left:8px}.JT9o0,.ZnIJV{align-items:center;border:1px solid var(–mXZkqc);border-radius:16px;box-sizing:border-box;color:#1a73e8;cursor:pointer;display:flex;height:32px;margin-bottom:16px}.BkHX0d{font-family:Google Sans,arial,sans-serif-medium,sans-serif;font-size:14px;line-height:20px;padding-right:20px;text-align:center;white-space:nowrap}.xv1D5b{display:block;padding:0 8px 0 12px;width:18px;height:18px}.LGOjhe{overflow:hidden;padding-bottom:20px}.trNcde .LGOjhe{overflow:visible}.SALvLe .LGOjhe,.Jb0Zif .LGOjhe,.HSryR .LGOjhe,.IVvPP .LGOjhe{padding:0 0 10px;margin:10px 0 0 0}.s6JM6d .SALvLe .LGOjhe{margin-top:12px;}.s6JM6d .HSryR .LGOjhe{margin-top:12px;padding-bottom:20px}#res .Jb0Zif .qDOt0b h3,.IVvPP .qDOt0b h3{font-size:16px;line-height:1.375}.Jb0Zif 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sup{line-height:0.9}.yuRUbf{font-weight:normal;font-size:small;line-height:1.58;}.IsZvec{max-width:48em;color:#4d5156;line-height:1.58}.uo4vr{color:var(–IXoxUe);line-height:1.58}.IjZ7ze{display:inline-block;color:var(–IXoxUe);font-size:12px;line-height:1.34;white-space:nowrap}.FyYA1e{margin:5px 0}a:hover h3.LC20lb{text-decoration:underline}.M8OgIe .dG2XIf .fm06If .LC20lb,.n6SJS h3.LC20lb{overflow:hidden;text-overflow:ellipsis;white-space:nowrap;width:100%}.LC20lb{display:inline-block;line-height:1.3;margin-bottom:3px;}.c2xzTb .LC20lb{margin-bottom:0}.MMgsKf{padding-top:2px}.DKV0Md{padding-top:4px;padding-top:5px;}.Z3xoIb{padding-top:27px;padding-top:28px;}.NXKJM{display:-webkit-box;overflow:hidden;-webkit-box-orient:vertical;-webkit-line-clamp:1}.hceuRc{-webkit-box-orient:vertical;display:-webkit-box;-webkit-line-clamp:2;overflow:hidden}.fzBvHb{font-weight:700}.DKV0Md,.Z3xoIb{margin-top:18px;}.xvfwl{margin-top:4px}.q0vns a.fl{font-size:12px}.TQc1id .qLRx3b{font-size:14px;line-height:1.58}.HGLrXd{display:inline-block;-webkit-text-size-adjust:none}.q0vns{display:inline-block;padding-bottom:2px;padding-top:1px}.NJjxre{position:absolute;left:0;top:0;width:100%}.M8OgIe .VWCdhc.Mjve0e .q0vns{width:max-content}.VjDLd .TieM1d .tjvcx,.IVvPP .tjvcx,.kno-kp .tjvcx,.VjDLd .kp-wholepage-osrp .tjvcx,#rhs .ss6qqb .tjvcx,#rhs .trNcde .tjvcx{display:inline-block;height:19px;overflow-y:hidden}.ojE3Fb{padding:0;padding-bottom:0;}.ojE3Fb .q0vns{display:flex;overflow:hidden;padding:0;padding-bottom:0;align-items:center;}.ojE3Fb .q0vns a.fl{padding-top:0;font-size:12px;line-height:18px;}.GvPZzd{font-size:12px;line-height:18px;}.dTxz9{padding-right:38px}.iG7WGe{color:#202124;padding:0;text-align:center;width:16px}.VuuXrf{color:#202124;font-size:14px;display:block;line-height:20px;white-space:nowrap;}.qncq2c{font-size:12px;line-height:16px;margin-left:6px}.CA5RN{overflow:hidden}.K2VDSb{display:flex;flex-direction:row}.H9lube{background-color:#f1f3f4;border:1px solid #dadce0;border-radius:50%;display:inline-flex;justify-content:center;align-items:center;height:26px;width:26px;margin-right:12px;flex-shrink:0;vertical-align:middle;}.fJOpI.H9lube{background-color:#e2eeff;border:1px solid #e2eeff}.P1UpZb{background-color:#f1f3f4;border:1px solid #ecedef}.eqA2re.NjwKYd{margin-right:0}.Vwoesf:not(.oRVWZ){display:inline-block}.Vwoesf{vertical-align:middle}.XNo5Ab.XNo5Ab{display:block;}.lWlVCe{border-radius:50%}.bJVp8c{color:#0060f0}.Jj3Uob{color:#0060f
0;}.ob9lvb{color:#4d5156}.ob9lvb.HCMUuf{color:var(–IXoxUe)}.ylgVCe{color:#4d5156}.B6fmyf{position:absolute;top:0;height:0;visibility:hidden;white-space:nowrap;width:100%}.B6fmyf.Mg1HEd{height:auto}.ljeAnf{display:-webkit-box;overflow:hidden;-webkit-box-orient:vertical}.byrV5b{align-items:center;display:flex;flex-direction:row}.sBJG1d{display:flex;flex-direction:row;justify-content:center}.kDmHO{align-items:center;display:flex;flex-direction:column}.lR4vec{display:flex;flex-direction:column;justify-content:center}.xTEyc{align-items:start;display:flex;flex-direction:row}.OjFzvd{display:flex;flex-direction:row;justify-content:start}.YIPhrb{align-items:start;display:flex;flex-direction:column}.BToiNc{display:flex;flex-direction:column;justify-content:start}.E4bmEc .Va021{flex:1 1 100%}.E4bmEc .Y76LGf{flex:1 1 calc(50% – 4px)}
Basically, it is a sequence of characters that are used in search patterns. It performs four basic types of operations: Validation: will determine if its pattern matches a string, returning a boolean. Extraction/Find: will look through a large string to find pieces that match its own pattern.

How can I write regular expression : .wDYxhc{clear:both}.cUnQKe .wDYxhc,.related-question-pair .wDYxhc,.M8OgIe .fm06If .wDYxhc{clear:none}html .dG2XIf .xpdclose .LKPcQc,html .dG2XIf .xpdopen .viOShc{padding-top:0;}.garHBe{color:var(–COEmY);font-size:20px;line-height:1.3;position:relative}.garHBe a{color:var(–COEmY)}.xpdopen .Hhmu2e{overflow:inherit}.xpdclose .a84NUc:not(:empty),.xpdopen .CQKTwc:not(:empty){border-top:solid 1px #ebebeb;border-radius:0}.xpdclose .pmYXee .a84NUc:not(:empty),.xpdopen .pmYXee .CQKTwc:not(:empty){border-top:none}.cAn2Qb .a84NUc:not(:empty),.cAn2Qb .CQKTwc:not(:empty){border-top:none}.SHa8ve{display:none}.xpdclose .TOfaBb.SHa8ve,.xpdopen .LL5J7d.SHa8ve{display:block}.rKR6H{padding-top:0.1px}.xpdclose .oHglmf,.xpdopen .xzPb7d{padding-bottom:16px}.xpdclose .kp-header .oHglmf,.xpdopen .kp-header .xzPb7d{padding-bottom:0}.c2xzTb .xpdclose .oHglmf,.c2xzTb .xpdopen .xzPb7d{padding-bottom:0}.HSryR .xpdclose .oHglmf,.HSryR .xpdopen .xzPb7d{padding-bottom:0}.Wnoohf .xpdopen .yp1CPe,.OJXvsb .xpdclose .siXlze{padding-bottom:16px}.Wnoohf .xpdopen .yp1CPe .xpdbox g-more-link{top:28px}.Wnoohf .xpdclose .wDYxhc.xsZWvb,.Wnoohf .xpdopen .wDYxhc.EfDVh{padding-bottom:0}.OJXvsb .xpdclose .wDYxhc.siXlze{padding-bottom:16px}#rhs .dG2XIf .xpdclose .LKPcQc,#rhs .dG2XIf .xpdopen .viOShc{padding-top:0}#rhs .Wnoohf .xpdopen .yp1CPe,#rhs .OJXvsb .xpdclose .siXlze{padding-bottom:15px}#rhs .Wnoohf .xpdclose .wDYxhc.xsZWvb,#rhs .Wnoohf .xpdopen .wDYxhc.EfDVh{padding-bottom:0}#rhs .Wnoohf .xpdclose .wDYxhc.xsZWvb.ecRggb,#rhs .Wnoohf .xpdopen .wDYxhc.EfDVh.ecRggb,#rhs .dG2XIf .ecRggb{padding-bottom:15px}.ecRggb{background-color:#fff;box-shadow:none;border:1px solid #dadce0;border-radius:8px;margin:0 0 16px 0}.tWSgNb .cAn2Qb{border-bottom:none}.IiOSLb .rsGxI.Ww4FFb,.Ww4FFb{background-color:var(–xhUGwc);border-radius:0px;border-width:0;box-shadow:none}.Ww4FFb .mnr-c:not(:empty),.mnr-c:not(:empty) .Ww4FFb,.Ww4FFb .Ww4FFb{box-shadow:none;margin-bottom:0px}.vt6azd{margin:0px 0px 8px}.vt6azd{margin:0px 0px 30px}.CBvvz{margin:-var(–sds-sys-measurement–space-sm) 0px 0px}.CBvvz{margin:-30px 0px 0px}.Jb0Zif .UiGGAb.ILfuVd,.ILfuVd{font-size:16px;line-height:24px;}.fm06If .ILfuVd.NA6bn,.c2xzTb .ILfuVd.duSGDe,.c2xzTb .ILfuVd.NA6bn.c3biWd{font-size:14px;line-height:1.58;}.c2xzTb .zloOqf{font-size:16px;margin-bottom:16px;margin-top:-8px;}.FLWspc{margin:16px}.LFYdN{font-size:16px;margin:16px}.trNcde .ILfuVd{color:var(–bbQxAb);font-family:Google Sans,arial,sans-serif;font-size:14px;line-height:22px}.HSryR .ILfuVd{line-height:1.5}.ss6qqb .ILfuVd,.ss6qqb .UiGGAb.ILfuVd{font-size:14px;line-height:22px}.c2xzTb .qLYAZd{margin:16px 16px 16px 0;}.d9FyLd{padding:0 0 10px}.hgKElc{padding:0 8px 0 0}.kX21rb{font-size:12px;line-height:1.34;display:inline-block;font-family:Google Sans,arial,sans-serif;padding-right:0;white-space:nowrap}.SPV4pd{display:flex;overflow-x:auto}.SPV4pd::-webkit-scrollbar{display:none}.Vjskue{margin-left:8px}.JT9o0,.ZnIJV{align-items:center;border:1px solid var(–mXZkqc);border-radius:16px;box-sizing:border-box;color:#1a73e8;cursor:pointer;display:flex;height:32px;margin-bottom:16px}.BkHX0d{font-family:Google Sans,arial,sans-serif-medium,sans-serif;font-size:14px;line-height:20px;padding-right:20px;text-align:center;white-space:nowrap}.xv1D5b{display:block;padding:0 8px 0 12px;width:18px;height:18px}.LGOjhe{overflow:hidden;padding-bottom:20px}.trNcde .LGOjhe{overflow:visible}.SALvLe .LGOjhe,.Jb0Zif .LGOjhe,.HSryR .LGOjhe,.IVvPP .LGOjhe{padding:0 0 10px;margin:10px 0 0 0}.s6JM6d .SALvLe .LGOjhe{margin-top:12px;}.s6JM6d .HSryR .LGOjhe{margin-top:12px;padding-bottom:20px}#res .Jb0Zif .qDOt0b h3,.IVvPP .qDOt0b h3{font-size:16px;line-height:1.375}.Jb0Zif .qDOt0b .iUh30,.IVvPP .qDOt0b .iUh30{font-size:14px;line-height:1.58}.IVvPP .qDOt0b{border-bottom:1px solid var(–gS5jXb);padding-bottom:6px}.rjOVwe.ILfuVd{font-size:16px;line-height:20px}.dG2XIf .rjOVwe{padding-top:22px;padding-bottom:0;margin-bottom:1px}.xWd7I{padding-top:12px;}.ILfuVd.NA6bn,.ILfuVd.duSGDe,.ILfuVd.UiGGAb,.IVvPP .ILfuVd{font-size:14px;line-height:22px}.n6SJS .ILfuVd{font-size:14px}.ILfuVd.NA6bn,.ILfuVd.duSGDe,.ILfuVd.UiGGAb,.IVvPP .ILfuVd{line-height:20px}.xpd-wa .g-blk{margin:initial}.xpd-wa .dG2XIf{border:initial;box-shadow:none}.fm06If .ILfuVd,.c2xzTb .ILfuVd,.Jb0Zif .c2xzTb .ILfuVd{font-family:Google Sans,arial,sans-serif;color:var(–YLNNHc)}.fm06If .ILfuVd,.c2xzTb .ILfuVd,.Jb0Zif .c2xzTb .ILfuVd{font-size:20px;line-height:28px}.cUnQKe .ILfuVd,.cUnQKe .UiGGAb.ILfuVd,.w5mTAe .ILfuVd,.W0urI .ILfuVd{color:var(–bbQxAb);font-family:Google Sans,arial,sans-serif;font-size:16px;line-height:24px}.fm06If .ILfuVd b,.trNcde .ILfuVd b,.cUnQKe .ILfuVd b,.c2xzTb .ILfuVd b,.w5mTAe .ILfuVd b,.W0urI .ILfuVd b{background-color:#d3e3fd;color:#040c28;font-weight:500}@media (forced-colors:active){.fm06If .ILfuVd b,.c2xzTb .ILfuVd b,.trNcde .ILfuVd b,.cUnQKe .ILfuVd b,.w5mTAe .ILfuVd b,.W0urI .ILfuVd b{background-color:Mark;color:MarkText}}.vBnbff .mO5MMe{padding-top:10px}.cUnQKe .vBnbff .mO5MMe{padding-left:0;}.trNcde .vBnbff .mO5MMe{padding:10px 0 0 0}.cAn2Qb.abzPbc .mnr-c{max-width:calc(100% – 162px)}.tF2Cxc{position:relative}.Jb0Zif .BDNLRc{margin:16px 16px -11px}.RUXr2d{display:inline}.MTB56{margin-right:12px;vertical-align:middle}.Pthbuf{display:flex;align-items:center}.m164Nd{vertical-align:middle;display:inline-block}.qpGQpf{clear:both;padding-top:6px}.aCOpRe{line-height:1.58;word-wrap:break-word}.aCOpRe sup{line-height:0.9}.yuRUbf{font-weight:normal;font-size:small;line-height:1.58;}.IsZvec{max-width:48em;color:#4d5156;line-height:1.58}.uo4vr{color:var(–IXoxUe);line-height:1.58}.IjZ7ze{display:inline-block;color:var(–IXoxUe);font-size:12px;line-height:1.34;white-space:nowrap}.FyYA1e{margin:5px 0}a:hover h3.LC20lb{text-decoration:underline}.M8OgIe .dG2XIf .fm06If .LC20lb,.n6SJS h3.LC20lb{overflow:hidden;text-overflow:ellipsis;white-space:nowrap;width:100%}.LC20lb{display:inline-block;line-height:1.3;margin-bottom:3px;}.c2xzTb .LC20lb{margin-bottom:0}.MMgsKf{padding-top:2px}.DKV0Md{padding-top:4px;padding-top:5px;}.Z3xoIb{padding-top:27px;padding-top:28px;}.NXKJM{display:-webkit-box;overflow:hidden;-webkit-box-orient:vertical;-webkit-line-clamp:1}.hceuRc{-webkit-box-orient:vertical;display:-webkit-box;-webkit-line-clamp:2;overflow:hidden}.fzBvHb{font-weight:700}.DKV0Md,.Z3xoIb{margin-top:18px;}.xvfwl{margin-top:4px}.q0vns a.fl{font-size:12px}.TQc1id .qLRx3b{font-size:14px;line-height:1.58}.HGLrXd{display:inline-block;-webkit-text-size-adjust:none}.q0vns{display:inline-block;padding-bottom:2px;padding-top:1px}.NJjxre{position:absolute;left:0;top:0;width:100%}.M8OgIe .VWCdhc.Mjve0e .q0vns{width:max-content}.VjDLd .TieM1d .tjvcx,.IVvPP .tjvcx,.kno-kp .tjvcx,.VjDLd .kp-wholepage-osrp .tjvcx,#rhs .ss6qqb .tjvcx,#rhs .trNcde .tjvcx{display:inline-block;height:19px;overflow-y:hidden}.ojE3Fb{padding:0;padding-bottom:0;}.ojE3Fb .q0vns{display:flex;overflow:hidden;padding:0;padding-bottom:0;align-items:center;}.ojE3Fb .q0vns a.fl{padding-top:0;font-size:12px;line-height:18px;}.GvPZzd{font-size:12px;line-height:18px;}.dTxz9{padding-right:38px}.iG7WGe{color:#202124;padding:0;text-align:center;width:16px}.VuuXrf{color:#202124;font-size:14px;display:block;line-height:20px;white-space:nowrap;}.qncq2c{font-size:12px;line-height:16px;margin-left:6px}.CA5RN{overflow:hidden}.K2VDSb{display:flex;flex-direction:row}.H9lube{background-color:#f1f3f4;border:1px solid #dadce0;border-radius:50%;display:inline-flex;justify-content:center;align-items:center;height:26px;width:26px;margin-right:12px;flex-shrink:0;vertical-align:middle;}.fJOpI.H9lube{background-color:#e2eeff;border:1px solid #e2eeff}.P1UpZb{background-color:#f1f3f4;border:1px solid #ecedef}.eqA2re.NjwKYd{margin-right:0}.Vwoesf:not(.oRVWZ){display:inline-block}.Vwoesf{vertical-align:middle}.XNo5Ab.XNo5Ab{display:block;}.lWlVCe{border-radius:50%}.bJVp8c{color:
#0060f0}.Jj3Uob{color:#0060f0;}.ob9lvb{color:#4d5156}.ob9lvb.HCMUuf{color:var(–IXoxUe)}.ylgVCe{color:#4d5156}.B6fmyf{position:absolute;top:0;height:0;visibility:hidden;white-space:nowrap;width:100%}.B6fmyf.Mg1HEd{height:auto}.ljeAnf{display:-webkit-box;overflow:hidden;-webkit-box-orient:vertical}.byrV5b{align-items:center;display:flex;flex-direction:row}.sBJG1d{display:flex;flex-direction:row;justify-content:center}.kDmHO{align-items:center;display:flex;flex-direction:column}.lR4vec{display:flex;flex-direction:column;justify-content:center}.xTEyc{align-items:start;display:flex;flex-direction:row}.OjFzvd{display:flex;flex-direction:row;justify-content:start}.YIPhrb{align-items:start;display:flex;flex-direction:column}.BToiNc{display:flex;flex-direction:column;justify-content:start}.E4bmEc .Va021{flex:1 1 100%}.E4bmEc .Y76LGf{flex:1 1 calc(50% – 4px)}
Writing a regular expression pattern. A regular expression pattern is composed of simple characters, such as /abc/ , or a combination of simple and special characters, such as /ab*c/ or /Chapter (\d+)\.\d*/ . The last example includes parentheses, which are used as a memory device.