c programming

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/* This incredibly useful tool is provided to help you * analyze your shell's job creation and management. * * Don't be afraid to build other simple tools (like this one) * to help you debug your shell as you develop Project 2. * * Compile using: * $ gcc -o job_info job_info.c * ********************************************************* * * Example Use Cases: * * * 1. You can use this tool to check if your shell is * putting jobs into process groups correctly: * * $ ./job_info | ./job_info | ./job_info | ./job_info * Terminal FG process group: 10648 * Command PID PPID PGID * 1 10648 10533 10648 * 2 10649 10533 10648 * 3 10650 10533 10648 * 4 10651 10533 10648 * ^C$ * ********************************************************* * * 2. You can check to see that the foreground process * group is being set correctly: * * $ ps -A | grep pssh * 12085 pts/28 00:00:00 pssh * * $ ./job_info | ./job_info | ./job_info | ./job_info & * [0] 12128 12129 12130 12131 * Terminal FG process group: 12085 * Command PID PPID PGID * 1 12128 12085 12128 * 2 12129 12085 12128 * 3 12130 12085 12128 * 4 12131 12085 12128 * * $ jobs * [0] + running ./job_info | ./job_info | ./job_info | ./job_info & * * $ fg %0 * Terminal FG process group: 12128 * Process 12130 (3) received signal 18 [Continued] * Process 12131 (4) received signal 18 [Continued] * Process 12128 (1) received signal 18 [Continued] * Process 12129 (2) received signal 18 [Continued] * * ^ZProcess 12130 (3) received signal 20 [Stopped] * Process 12129 (2) received signal 20 [Stopped] * Process 12131 (4) received signal 20 [Stopped] * Terminal FG process group: 12128 * Process 12128 (1) received signal 20 [Stopped] * [0] + suspended ./job_info | ./job_info | ./job_info | ./job_info & * * $ bg %0 * [0] + continued ./job_info | ./job_info | ./job_info | ./job_info & * Terminal FG process group: 12085 * Process 12128 (1) received signal 18 [Continued]

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* Process 12131 (4) received signal 18 [Continued] * Process 12130 (3) received signal 18 [Continued] * Process 12129 (2) received signal 18 [Continued] * * $ kill %0 * [0] + done ./job_info | ./job_info | ./job_info | ./job_info & * $ */

#include <unistd.h> #include <stdio.h> #include <string.h> #include <signal.h>

static int cmd_num;

static void handler (int sig) { if (getpid() == getpgrp()) fprintf (stderr, "Terminal FG process group: %i\n", tcgetpgrp (STDIN_FILENO));

fprintf (stderr, "Process %i (%i) received signal %i [%s]\n", getpid(), cmd_num, sig, strsignal (sig));

if (sig == SIGTSTP) raise (SIGSTOP); }

int main (int argc, char** argv) { struct sigaction sa;

sigemptyset (&sa.sa_mask); sa.sa_flags = SA_RESTART; sa.sa_handler = handler;

sigaction (SIGTSTP, &sa, NULL); sigaction (SIGCONT, &sa, NULL);

if (isatty (STDIN_FILENO)) { fprintf (stderr, "Terminal FG process group: %i\n", tcgetpgrp (STDIN_FILENO));

fprintf (stderr, "Command PID PPID PGID\n"); cmd_num = 0; } else { read (STDIN_FILENO, &cmd_num, sizeof(cmd_num)); }

cmd_num++;

fprintf (stderr, " %4i %5i %5i %5i\n", cmd_num, getpid(), getppid(), getpgrp());

if (!isatty (STDOUT_FILENO)) write (STDOUT_FILENO, &cmd_num, sizeof(cmd_num));

while (1) pause ();

}