C programming- Regex matching and store in string

Question

I am able to match patterns using regex library in C. The matched words can be printed. But, i need to store the matches into a string or char array. The code is below:

void match(regex_t *pexp, char *sz) {
regmatch_t matches[MAX_MATCHES]; //A list of the matches in the string (a list of 1)
  if (regexec(pexp, sz, MAX_MATCHES, matches, 0) == 0) 
  {
    printf("%.*s\n", (int)(matches[0].rm_eo - matches[0].rm_so), sz + matches[0].rm_so);        
  }
  else {
    printf("\"%s\" does not match\n", sz);
   }
 }

int main() {
int rv;
regex_t exp;
rv = regcomp(&exp, "-?([A-Z]+)", REG_EXTENDED);
if (rv != 0) {
    printf("regcomp failed with %d\n", rv);
}
match(&exp, "456-CCIMI");
regfree(&exp);
return 0;
}

OR may be just i need this. How can i splice char array in C? ie. if a char array has "ABCDEF" 6 characters. I just need the chars in index 2 to index 5 "CDEF".

jogh · Accepted Answer · 2014-04-03 11:27:30Z

3

For the example you provided, if you want -CCIMI, you can

strncpy(dest, sz + matches[0].rm_so, matches[0].rm_eo - matches[0].rm_so);

But since you used group in pattern, I guess what you really want is just CCIMI. You can

strncpy(dest, sz + matches[1].rm_so, matches[1].rm_eo - matches[1].rm_so);

Before strncpy(), please do malloc sufficient space for dest

answered Apr 3, 2014 at 11:27

jogh

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1 Comment

Some programmer dude Over a year ago

Be aware that strncpy may not add the string terminator.

Some programmer dude · Accepted Answer · 2014-04-03 10:49:41Z

1

You can use memcpy to copy the matched string to an array, or dynamically allocate a string:

char *dest;

/* your regexec call */

dest = malloc(matches[0].rm_eo - matches[0].rm_so + 1);  /* +1 for terminator */

memcpy(dest, sz + matches[0].rm_so, matches[0].rm_eo - matches[0].rm_so);

dest[matches[0].rm_eo - matches[0].rm_so] = '\0';  /* terminate the string */

After the above code, dest points to the matched string.

answered Apr 3, 2014 at 10:49

Some programmer dude

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2 Comments

gzix Over a year ago

i am getting this warning while compiling "incompatible implicit declaration of built-in function ‘malloc’"

Some programmer dude Over a year ago

@user2943851 Any decent reference for malloc will tell you what header file you need to include.

Nish · Accepted Answer · 2014-04-03 11:00:30Z

0

you can use strncpy also, if you are looking for a string function.

strncpy(dest, sz + matches[0].rm_so, matches[0].rm_eo - matches[0].rm_so);

answered Apr 3, 2014 at 11:00

Nish

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1 Comment

Some programmer dude Over a year ago

Be aware that strncpy may not add the string terminator.

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