Simple helper that checks if Linux filesystem capabilites() are set without using external libraries.

gistfile1.c

#include <sys/types.h>
#include <sys/xattr.h>
#include <errno.h>

#include <stdio.h>
#include <stdlib.h>

/*
 * A quick and dirty test to see if a given file has any Linux capabilities
 * set.
 *
 * usage: has_caps filename
 *
 * Returns:
 *   1 - has capabilites 
 *   0 - no capabilities
 *  -1 - usage/internal error
 */

int main(int argc, char *argv[]) {
  const char *security_capability = "security.capability";
  const char *path = NULL;
  ssize_t len;

  if (argc != 2) {
    return -1;
  }

  path = argv[1];
  len = getxattr(path, security_capability, NULL, 0);
  if (len == -1) {
    switch (errno) {
    case ENODATA:
      /* There are no capabilities set. */
      return 0;
    case ENOTSUP:
      /* The file system does not support capabilities. */
      return 0;
    default:
      /* File not found, etc (hard fail). */
      return -1;
    }
  } else if (len == 0) {
    /* Shouldn't happen (ENODATA), but treat it as if none are set. */
    return 0;
  }

  return 1;
}