Thread: Question about regular expression

Hi all,

I'm new to C program, and I have some coding problems which is about regex.h.

I'm trying to find the matching pattern "-w[0-9]*" in the string. But I just couldn't figure out
what should I put in regcomp brackets.

Can someone please tell me?

regcomp function is used to compile a regular expression into a form to be used by the subsequent regexec function.

Actually,regexec function only used to match the pattern.

If you want to match the -w[0-9]* string.Then,you use the following program.

Code:

#include <regex.h>  //including the functions for matching regular expressions                                                                                                                
#include <stdio.h>   //including the standard functions                                                           
#include <stdlib.h>  //including the standard library functions                                                           
                                                                                
main() {                                                                        
    regex_t    preg;    //creating the                                                         
    char       *string = "-w1";                                     
    char       *pattern = "-w[0-9]*";                                       
    int        rc;                                                              
    size_t     nmatch = 2;   //nmatch and pmatch are used  to provide informations about the matches                                                  
    regmatch_t pmatch[2];                                                       
                                                                                
    if ((rc = regcomp(&preg, pattern, REG_EXTENDED)) != 0) {  //giving the pattern string                    to regcomp function to make the string pattern in the form to match by regexec function 
       printf("regcomp() failed, returning nonzero (%d)\n", rc);                
       //exit(1);                                                                 
    }                                                                           
                                                                                
    if ((rc = regexec(&preg, string, nmatch, pmatch, 0)) != 0) {   //matching the regular expression             
       printf("failed to ERE match '%s' with '%s',returning %d.\n",             
       string, pattern, rc);                                                    
    }                                                                           
    // Both the functions on success,returns 0.
    else if(rc==0)
	    printf ( "Pattern Matched\n" );
    regfree(&preg);                                                             
}

Code:

        regex_t re;
        char patt[]="-w[0-9]*";
        char string[]="-w100";
        int status;
        regcomp(&re,patt,REG_EXTENDED);
        status=regexec(&re,string,(size_t)0,NULL,0);

regexec() will return zero for successful match.

ty.. Im trying to figure out how do those functions work =)