Format
#include <regex.h> int regcomp(regex_t *preg, const char *pattern, int cflags);
Language Level: XPG4
Threadsafe: Yes.
Locale Sensitive: The behavior of this function might be affected by the LC_CTYPE and LC_COLLATE categories of the current locale. This function is not available when LOCALETYPE(*CLD) is specified on the compilation command. For more information, see Understanding CCSIDs and Locales.
Description
The regcomp() function compiles the source regular expression pointed to by pattern into an executable version and stores it in the location pointed to by preg. You can then use the regexec()function to compare the regular expression to other strings.
The cflags flag defines the attributes of the compilation process:
Regular expressions are a context-independent syntax that can represent a wide variety of character sets and character set orderings, which can be interpreted differently depending on the current locale. The functions regcomp(), regerror(), regexec(), and regfree() use regular expressions in a similar way to the UNIX® awk, ed, grep, and egrep commands.
Return Value
If the regcomp() function is successful, it returns 0. Otherwise, it returns an error code that you can use in a call to the regerror() function, and the content of preg is undefined.
Example that uses regcomp()
#include <regex.h>
#include <stdio.h>
#include <stdlib.h>
int main(void)
{
regex_t preg;
char *string = "a very simple simple simple string";
char *pattern = "\\(sim[a-z]le\\) \\1";
int rc;
size_t nmatch = 2;
regmatch_t pmatch[2];
if (0 != (rc = regcomp(&preg, pattern, 0))) {
printf("regcomp() failed, returning nonzero (%d)\n", rc);
exit(EXIT_FAILURE);
}
if (0 != (rc = regexec(&preg, string, nmatch, pmatch, 0))) {
printf("Failed to match '%s' with '%s',returning %d.\n",
string, pattern, rc);
}
else {
printf("With the whole expression, "
"a matched substring \"%.*s\" is found at position %d to %d.\n",
pmatch[0].rm_eo - pmatch[0].rm_so, &string[pmatch[0].rm_so],
pmatch[0].rm_so, pmatch[0].rm_eo - 1);
printf("With the sub-expression, "
"a matched substring \"%.*s\" is found at position %d to %d.\n",
pmatch[1].rm_eo - pmatch[1].rm_so, string[pmatch[1].rm_so],
pmatch[1].rm_so, pmatch[1].rm_eo - 1);
}
regfree(&preg);
return 0;
/****************************************************************************
The output should be similar to :
With the whole expression, a matched substring "simple simple" is found
at position 7 to 19.
With the sub-expression, a matched substring "simple" is found
at position 7 to 12.
****************************************************************************/
}Related Information