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| <tr><td width=20><td><b>REGEXP(7)</b><td align=right><b>REGEXP(7)</b> |
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| <p><font size=+1><b>NAME </b></font><br> |
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| regexp – Plan 9 regular expression notation<br> |
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| <p><font size=+1><b>DESCRIPTION </b></font><br> |
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| This manual page describes the regular expression syntax used |
| by the Plan 9 regular expression library <a href="../man3/regexp.html"><i>regexp</i>(3)</a>. It is the |
| form used by <a href="../man1/egrep.html"><i>egrep</i>(1)</a> before <i>egrep</i> got complicated. |
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| A <i>regular expression</i> specifies a set of strings of characters. |
| A member of this set of strings is said to be <i>matched</i> by the regular |
| expression. In many applications a delimiter character, commonly |
| <tt><font size=+1>/</font></tt>, bounds a regular expression. In the following specification |
| for regular expressions the word ‘character’ means any |
| character (rune) but newline. |
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| The syntax for a regular expression <tt><font size=+1>e0</font></tt> is<br> |
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| <tt><font size=+1>e3: literal | charclass | '.' | '^' | '$' | '(' e0 ')'<br> |
| e2: e3<br> |
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| | e2 REP<br> |
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| REP: '*' | '+' | '?'<br> |
| e1: e2<br> |
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| | e1 e2<br> |
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| e0: e1<br> |
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| | e0 '|' e1<br> |
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| </font></tt> |
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| A <tt><font size=+1>literal</font></tt> is any non-metacharacter, or a metacharacter (one of |
| <tt><font size=+1>.*+?[]()|\^$</font></tt>), or the delimiter preceded by <tt><font size=+1>\</font></tt>. |
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| A <tt><font size=+1>charclass</font></tt> is a nonempty string <i>s</i> bracketed <tt><font size=+1>[</font></tt><i>s</i><tt><font size=+1>]</font></tt> (or <tt><font size=+1>[^</font></tt><i>s</i><tt><font size=+1>]</font></tt>); it |
| matches any character in (or not in) <i>s</i>. A negated character class |
| never matches newline. A substring <i>a</i><tt><font size=+1>−</font></tt><i>b</i>, with <i>a</i> and <i>b</i> in ascending |
| order, stands for the inclusive range of characters between <i>a</i> |
| and <i>b</i>. In <i>s</i>, the metacharacters <tt><font size=+1>−</font></tt>, <tt><font size=+1>]</font></tt>, an initial <tt><font size=+1>^</font></tt>, and the |
| regular expression delimiter must be preceded by a <tt><font size=+1>\</font></tt>; other metacharacters |
| have no special meaning and may appear unescaped. |
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| A <tt><font size=+1>.</font></tt> matches any character. |
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| A <tt><font size=+1>^</font></tt> matches the beginning of a line; <tt><font size=+1>$</font></tt> matches the end of the |
| line. |
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| The <tt><font size=+1>REP</font></tt> operators match zero or more (<tt><font size=+1>*</font></tt>), one or more (<tt><font size=+1>+</font></tt>), zero |
| or one (<tt><font size=+1>?</font></tt>), instances respectively of the preceding regular expression |
| <tt><font size=+1>e2</font></tt>. |
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| A concatenated regular expression, <tt><font size=+1>e1e2</font></tt>, matches a match to <tt><font size=+1>e1</font></tt> |
| followed by a match to <tt><font size=+1>e2</font></tt>. |
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| An alternative regular expression, <tt><font size=+1>e0|e1</font></tt>, matches either a match |
| to <tt><font size=+1>e0</font></tt> or a match to <tt><font size=+1>e1</font></tt>. |
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| A match to any part of a regular expression extends as far as |
| possible without preventing a match to the remainder of the regular |
| expression.<br> |
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| <p><font size=+1><b>SEE ALSO </b></font><br> |
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| <a href="../man3/regexp.html"><i>regexp</i>(3)</a><br> |
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