In C, checking for existence of file with name matching a pattern

Question

I've seen a few methods for checking the existence of a file in C. However, everything I've seen works for a specific file name. I would like to check for any file that matches a particular pattern. For instance, maybe the pattern is "lockfile*" and "lockfileA", "lockfile.txt", or "lockfile.abc" would register in the check. The way I am doing this currently is to open the directory with opendir() then cycle through readdir() and try to match the pattern with name of each file returned. It works, but I sure would like a more compact way to do this. Any ideas?

Answer 1

You can use glob(3) (standardized by POSIX). You give it a wildcard pattern and it will search the filesystem for matches.

Example:

#include <glob.h>
#include <stdio.h>

int main(int argc, char **argv)
{
   glob_t globbuf;
   if (0==glob(argv[1], 0, NULL, &globbuf)){
       char **a=globbuf.gl_pathv;

       puts("MATCHES");
       for(;*a;a++)
           puts(*a);
   }
   globfree(&globbuf);
}

Running:

./a.out 'lockfile*'

should give you your lockfiles.

Answer 2

To my knowledge, that's how it should be done.

For each name d_name of the file, you can check it's length and if it has at least 8 characters, strcmp that 8 first characters to lockfile.

You can also use <regex.h> for that check.

As for the iteration, I believe that's he best way to go.