set_nofile_limit.c

#define _GNU_SOURCE
#define _FILE_OFFSET_BITS 64
#include <stdio.h>
#include <time.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/resource.h>

#define errExit(msg) do { perror(msg); exit(EXIT_FAILURE); \ 
 } while (0)

int 
main(int argc, char *argv[]) {
  struct rlimit old, new;
  struct rlimit *newp;
  pid_t pid;

  if (!(argc == 2 || argc == 4)) {
    fprintf(stderr, "Usage: %s <pid> [<new-soft-limit> "
        "<new-hard-limit>]\n", argv[0]);
    exit(EXIT_FAILURE);
  }

  pid = atoi(argv[1]); /* PID of target process */

  newp = NULL;
  if (argc == 4) {
    new.rlim_cur = atoi(argv[2]);
    new.rlim_max = atoi(argv[3]);
    newp = &new;
  }

  if (prlimit(pid, RLIMIT_NOFILE, newp, &old) == -1)
    errExit("prlimit-1");
  printf("Previous limits: soft=%lld; hard=%lld\n",
      (long long) old.rlim_cur, (long long) old.rlim_max);

  if (prlimit(pid, RLIMIT_NOFILE, NULL, &old) == -1)
    errExit("prlimit-2");
  printf("New limits: soft=%lld; hard=%lld\n",
      (long long) old.rlim_cur, (long long) old.rlim_max);

  exit(EXIT_FAILURE);
}