#include <limits.h>
#include <stdio.h>
#include <string.h>
#include <unistd.h>

/* Finds the path containing the currently running program executable.
  The path is placed into BUFFER, which is of length LEN. Returns
  the number of characters in the path, or -1 on error. */

size_t get_executable_path (char* buffer, size_t len)
{
 char* path_end;
 /* Read the target of /proc/self/exe. */
 if (readlink ("/proc/self/exe", buffer, len) <= 0)
  return -1;
 /* Find the last occurrence of a forward slash, the path separator. */
 path_end = strrchr (buffer, '/');
 if (path_end == NULL)
  return -1;
 /* Advance to the character past the last slash. */
 ++path_end;
 /* Obtain the directory containing the program by truncating the
   path after the last slash. */
 *path_end = '\0';
 /* The length of the path is the number of characters up through the
   last slash. */
 return (size_t) (path_end - buffer);
}

int main ()
{
 char path[PATH_MAX];
 get_executable_path (path, sizeof (path));
 printf ("this program is in the directory %s\n", path);
 return 0;
}