libseccomp example. use `gcc test_seccomp.c -lseccomp` to compile

gistfile1.c

#include <stdio.h>
#include <stdlib.h>
#include <seccomp.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <errno.h>

int main()
{
    FILE *f1;
    int fd;
    int ret;
    scmp_filter_ctx ctx;

    f1 = fopen("/tmp/test1", "w");

    ctx = seccomp_init(SCMP_ACT_ERRNO(5));

    ret = seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(close), 0);
    if (!ret)
        ret = seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(dup), 0);
    if (!ret)
        ret = seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(write), 0);
    if (!ret)
        ret = seccomp_rule_add(ctx, SCMP_ACT_ALLOW, SCMP_SYS(exit), 0);
    if (!ret)
        ret = seccomp_load(ctx);
    if (ret)
        printf("error setting seccomp\n");

    fprintf(f1, "hi there\n");
    fd = open("/tmp/test2", O_RDWR);
    if (fd >= 0)
        printf("error, was able to open f2\n");
    else
        fprintf(f1, "open returned %d errno %d\n", fd, errno);
    fclose(f1);
    exit(0);
}

ref:
http://lwn.net/Articles/332974/
http://s3hh.wordpress.com/2012/07/24/playing-with-seccomp/