ghetto_prlimit.c

#include <sys/time.h>
#include <sys/resource.h>
#include <sys/types.h>
#include <stdio.h>
#include <string.h>

int main(int argc, char **argv) {
  if (argc < 2) {
    fprintf(stderr, "usage: %s [pid]", argv[0]);
    return 1;
  }

  pid_t pid = atoi(argv[1]);
  struct rlimit new_limit, old_limit;
  
  // Max open files
  new_limit.rlim_cur = 100000; // Soft
  new_limit.rlim_max = 500000; // Hard

  int ret = prlimit(pid, RLIMIT_NOFILE, &new_limit, &old_limit);
  if (ret == 0) {
    printf("Changed %i nofile limit from %u/%u to %u/%u\n", pid,
           old_limit.rlim_cur, old_limit.rlim_max,
           new_limit.rlim_cur, new_limit.rlim_max);
  } else {
    perror("prlimit");
  }

  return 0;
}