#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <unistd.h>
#include <signal.h>
#include <errno.h>
#include <sys/types.h>
#include <sys/wait.h>
static pid_t child_pid;
static void usage(void)
{
printf("usage: timelimit <time> <command>\n");
printf(" SIGUSR1 - passes SIGTERM to command's process group\n");
printf(" SIGALRM - passes SIGTERM to command's process group\n");
printf(" after 5s SIGKILL will be passed and exit(1)\n");
printf(" SIGTERM - passes SIGTERM to command's process group\n");
printf(" after 1s SIGKILL will be passed and exit(1)\n");
}
static void sig_alrm_kill(int sig)
{
fprintf(stderr, "\nMaximum time expired in timelimit - killing\n");
kill(-child_pid, SIGKILL);
exit(1);
}
static void sig_alrm_term(int sig)
{
kill(-child_pid, SIGTERM);
alarm(5);
signal(SIGALRM, sig_alrm_kill);
}
static void sig_term(int sig)
{
kill(-child_pid, SIGTERM);
alarm(1);
signal(SIGALRM, sig_alrm_kill);
}
static void sig_usr1(int sig)
{
kill(-child_pid, SIGTERM);
}
static void new_process_group(void)
{
if (setpgid(0,0) == -1) {
perror("setpgid");
exit(1);
}
}
int main(int argc, char *argv[])
{
int maxtime, ret=1;
if (argc < 3) {
usage();
exit(1);
}
maxtime = atoi(argv[1]);
child_pid = fork();
if (child_pid == 0) {
new_process_group();
execvp(argv[2], argv+2);
perror(argv[2]);
exit(1);
}
signal(SIGTERM, sig_term);
signal(SIGUSR1, sig_usr1);
signal(SIGALRM, sig_alrm_term);
alarm(maxtime);
do {
int status;
pid_t pid = wait(&status);
if (pid != -1) {
ret = WEXITSTATUS(status);
} else if (errno == ECHILD) {
break;
}
} while (1);
kill(-child_pid, SIGKILL);
exit(ret);
}