regcomp - Compile Regular Expression

Syntax

#include <sys/types.h>
#include <regex.h>
int regcomp(regex_t *preg, const char *pattern, int cflags);

Description

regcomp 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 regexec to compare the regular expression to other strings.

The cflags flag defines the attributes of the compilation process:

REG_EXTENDED

Support extended regular expressions.
REG_ICASE
Ignore case in match.
REG_NEWLINE
Treat new-line character as a special end-of-line character; it then establishes the line boundaries matched by the ^ and $ patterns, and can only be matched within a string explicitly using \n. (If you omit this flag, the new-line character is treated like any other character.)
REG_NOSUB
Ignore the number of subexpressions specified in pattern. When you compare a string to the compiled pattern (using regexec), the string must match the entire pattern. regexec then returns a value that indicates only if a match was found; it does not indicate at what point in the string the match begins, or what the matching string is.

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. Regular expressions are described in more detail under "Regular Expressions" in the VisualAge C++ Programming Guide.

Returns

If regcomp is successful, it returns 0. Otherwise, it returns an error code that you can use in a call to regerror, and the content of preg is undefined.

Example Code

This example compiles an extended regular expression.

#include <sys/types.h>#include <regex.h>
#include <stdio.h>
#include <stdlib.h>

int main(void)
{
   regex_t preg;
   char    *pattern = ".*(simple).*";
   int     rc;

   if (0 != (rc = regcomp(&preg, pattern, REG_EXTENDED))) {
      printf("regcomp() failed, returning nonzero (%d)\n", rc);
      exit(EXIT_FAILURE);
   }
   printf("regcomp() is sucessful.\n");
   return 0;

   /****************************************************************************
      The output should be similar to :

      regcomp() is sucessful.
   ****************************************************************************/
}

Related Information

• regerror
  
• regexec
  
• regfree

---

[Back: realloc - Change Reserved Storage Block Size]
[Next: regerror - Return Error Message for Regular Expression]