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POParent process killing child process in infinite loop
 

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  1. POParent process killing child process in infinite loop
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    <p>To solve my problem, I set <code>prctl(PR_SET_PDEATHSIG, SIGHUP);</code> as in <a href="https://stackoverflow.com/questions/284325/how-to-make-child-process-die-after-parent-exits">stackoverflow answer</a> before i called <code>exec*</code>, and took out the part where we pipe the PID. It works!!!!! Wow....</p> <p>HOWEVER, stackoverflow won't let me say I've answered my own question yet...</p> <p>So I tried to write a program, which I want to run a program, and kill that program after a cpl seconds if it doesn't finish. DADDY forks off a CHILD, which forks off another BABY, CHILD pipes the PID of the BABY to DADDY, which then waits a second and kills them both if they haven't wrapped up their business (it's a macabre scene). But it doesn't work, DADDY stays in S+ State, and the infinite loop that is Baby goes on forever until I ctr+c. On the bright side, this code is an amalgamation of everything I've learnt on stack-overflow. Here we go.</p> <pre><code>#include &lt;math.h&gt; #include &lt;signal.h&gt; #include &lt;stdint.h&gt; #include &lt;stdio.h&gt; #include &lt;stdlib.h&gt; #include &lt;string.h&gt; #include &lt;time.h&gt; #include &lt;unistd.h&gt; static int read_from_pipe(int file) { int c; FILE *stream = fdopen(file, "r"); if (fscanf(stream, "%d", &amp;c) != 1) { fprintf(stderr, "Failed to read integer from pipe\n"); exit(1); } fclose(stream); return c; } static void write_to_pipe(int file, int pidRacket) { FILE *stream = fdopen(file, "w"); fprintf(stream, "%d", pidRacket); fclose(stream); } static int spawnpipe(char *fileName, int *fd) { int pid; int pipe_fds[2]; char *command[] = {"racket", fileName, NULL}; if (pipe(pipe_fds) &lt; 0) { fprintf(stderr, "FE: pipe\n"); exit(1); } switch ((pid = fork())) { case -1: printf("syserr"); exit(1); case 0: close(1); close(2); dup(pipe_fds[1]); close(pipe_fds[0]); close(pipe_fds[1]); execvp(*command, command); perror("execv"); exit(EXIT_FAILURE); default: *fd = pipe_fds[0]; close(pipe_fds[1]); return pid; } } static int spawnfp(char *fileName, FILE **fpp) { int fd, pid; pid = spawnpipe(fileName, &amp;fd); *fpp = fdopen(fd, "r"); return pid; } int main(int argc, char *argv[]) { pid_t pid; int mypipe[2]; if (pipe(mypipe)) { fprintf(stderr, "Pipe failed.\n"); return EXIT_FAILURE; } pid = fork(); if (pid &lt; (pid_t) 0) { fprintf(stderr, "Fork failed.\n"); return EXIT_FAILURE; } else if (pid != (pid_t) 0) { double diff = 0; clock_t launch = clock(); close(mypipe[1]); int pidRacket = read_from_pipe(mypipe[0]); while (diff &lt; 1.3) { clock_t done = clock(); diff = ((double)done - (double)launch) / (double)CLOCKS_PER_SEC; } kill(pidRacket, SIGKILL); kill(pid, SIGKILL); return EXIT_SUCCESS; } else if (pid == (pid_t) 0) { close(mypipe[0]); char buf[100]; FILE *fp; char *fileName = argv[1]; int pidRacket = spawnfp(fileName, &amp;fp); write_to_pipe(mypipe[1], pidRacket); if (argc == 1) { printf("Not enough arguments!"); _exit(EXIT_FAILURE); } else if (argc == 2) { } sleep(1); while (fgets(buf, sizeof buf, fp)) { printf("%s\n", buf); } fclose(fp); kill(pid, SIGKILL); return 0; } } </code></pre> <p>Credit to quinsley and vijay!</p>
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