Revised snippet from prlimit(2)

limits.c

#define _GNU_SOURCE
#define _FILE_OFFSET_BITS 64
#include <stdio.h>
#include <time.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.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;
    char *limit;
    int reslimit;
    pid_t pid;

    if (!(argc == 3 || argc == 5)) {
        fprintf(stderr, "Usage: %s <LIMIT_TYPE> <pid> [<new-soft-limit> "
                "<new-hard-limit>]\n", argv[0]);
        exit(EXIT_FAILURE);
    }

    limit = argv[1];
    pid = atoi(argv[2]);        /* PID of target process */

    if (strcmp(limit, "NOFILE") == 0)
    { 
        reslimit = RLIMIT_NOFILE;
    }
    else if (strcmp(limit, "AS") == 0)
    {
        reslimit = RLIMIT_AS;
    }
    else if (strcmp(limit, "CORE") == 0)
    {
        reslimit = RLIMIT_CORE;
    }
    else if (strcmp(limit, "CPU") == 0)
    {
        reslimit = RLIMIT_CPU;
    }
    else if (strcmp(limit, "DATA") == 0)
    {
        reslimit = RLIMIT_DATA;
    }
    else if (strcmp(limit, "FSIZE") == 0)
    {
        reslimit = RLIMIT_FSIZE;
    }
    else if (strcmp(limit, "LOCKS") == 0)
    {
        reslimit = RLIMIT_LOCKS;
    }
    else if (strcmp(limit, "MEMLOCK") == 0)
    {
        reslimit = RLIMIT_MEMLOCK;
    }
    else if (strcmp(limit, "MSGQUEUE") == 0)
    {
        reslimit = RLIMIT_MSGQUEUE;
    }
    else if (strcmp(limit, "NICE") == 0)
    {
        reslimit = RLIMIT_NICE;
    }
    else if (strcmp(limit, "NPROC") == 0)
    {
        reslimit = RLIMIT_NPROC;
    }
    else if (strcmp(limit, "RSS") == 0)
    {
        reslimit = RLIMIT_RSS;
    }
    else if (strcmp(limit, "RTPRIO") == 0)
    {
        reslimit = RLIMIT_RTPRIO;
    }
    else if (strcmp(limit, "RTTIME") == 0)
    {
        reslimit = RLIMIT_RTTIME;
    }
    else if (strcmp(limit, "SIGPENDING") == 0)
    {
        reslimit = RLIMIT_SIGPENDING;
    }
    else if (strcmp(limit, "STACK") == 0)
    {
        reslimit = RLIMIT_STACK;
    }

    
    newp = NULL;
    if (argc == 5) {
        new.rlim_cur = atoi(argv[3]);
        new.rlim_max = atoi(argv[4]);
        newp = &new;
    }

    if (prlimit(pid, reslimit, 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, reslimit, 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_SUCCESS);
}