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| <h4 class="subsection">10.3.3 Matching a Compiled POSIX Regular Expression</h4> |
| |
| <p>Once you have compiled a regular expression, as described in <a href="POSIX-Regexp-Compilation.html#POSIX-Regexp-Compilation">POSIX Regexp Compilation</a>, you can match it against strings using |
| <code>regexec</code>. A match anywhere inside the string counts as success, |
| unless the regular expression contains anchor characters (‘<samp><span class="samp">^</span></samp>’ or |
| ‘<samp><span class="samp">$</span></samp>’). |
| |
| <!-- regex.h --> |
| <!-- POSIX.2 --> |
| <div class="defun"> |
| — Function: int <b>regexec</b> (<var>const regex_t *restrict compiled, const char *restrict string, size_t nmatch, regmatch_t matchptr</var>[<var>restrict</var>]<var>, int eflags</var>)<var><a name="index-regexec-879"></a></var><br> |
| <blockquote><p>This function tries to match the compiled regular expression |
| <code>*</code><var>compiled</var> against <var>string</var>. |
| |
| <p><code>regexec</code> returns <code>0</code> if the regular expression matches; |
| otherwise, it returns a nonzero value. See the table below for |
| what nonzero values mean. You can use <code>regerror</code> to produce an |
| error message string describing the reason for a nonzero value; |
| see <a href="Regexp-Cleanup.html#Regexp-Cleanup">Regexp Cleanup</a>. |
| |
| <p>The argument <var>eflags</var> is a word of bit flags that enable various |
| options. |
| |
| <p>If you want to get information about what part of <var>string</var> actually |
| matched the regular expression or its subexpressions, use the arguments |
| <var>matchptr</var> and <var>nmatch</var>. Otherwise, pass <code>0</code> for |
| <var>nmatch</var>, and <code>NULL</code> for <var>matchptr</var>. See <a href="Regexp-Subexpressions.html#Regexp-Subexpressions">Regexp Subexpressions</a>. |
| </p></blockquote></div> |
| |
| <p>You must match the regular expression with the same set of current |
| locales that were in effect when you compiled the regular expression. |
| |
| <p>The function <code>regexec</code> accepts the following flags in the |
| <var>eflags</var> argument: |
| |
| <dl> |
| <!-- regex.h --> |
| <!-- POSIX.2 --> |
| <dt><code>REG_NOTBOL</code><dd>Do not regard the beginning of the specified string as the beginning of |
| a line; more generally, don't make any assumptions about what text might |
| precede it. |
| |
| <!-- regex.h --> |
| <!-- POSIX.2 --> |
| <br><dt><code>REG_NOTEOL</code><dd>Do not regard the end of the specified string as the end of a line; more |
| generally, don't make any assumptions about what text might follow it. |
| </dl> |
| |
| <p>Here are the possible nonzero values that <code>regexec</code> can return: |
| |
| <dl> |
| <!-- regex.h --> |
| <!-- POSIX.2 --> |
| <dt><code>REG_NOMATCH</code><dd>The pattern didn't match the string. This isn't really an error. |
| |
| <!-- regex.h --> |
| <!-- POSIX.2 --> |
| <br><dt><code>REG_ESPACE</code><dd><code>regexec</code> ran out of memory. |
| </dl> |
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