Why is the kill process not working using the Exec function in my C program?-CodePudding

I am creating my own shell (like bash) and I have a function that calls the execv function and passes in a specific process pid to kill. I basically run a sleep command for 10 seconds, and halfway through I want to kill it. But my kill command does not seem to be working. Does anyone have any ideas how I can fix it?

Below are functions related to execv

void run_execv(char *path, char *args[])
{
    int result = execv(path, args);
}

void kill_process(char *target_pid)
{
    char *bin_path = "/bin/kill";
    char *args[] = {bin_path, "-15", target_pid, NULL};
    run_execv(bin_path, args);
}

void ps()
{
    char *bin_path = "/bin/ps";
    char *args[] = {bin_path, NULL};
    run_execv(bin_path, args);
}

And the calling of the kill_process function is shown below. Basically I am calling the kill command as a child process.

else if (strncmp(shellInput, "pkill", strlen("pkill")) == 0 || strncmp(shellInput, "kill", strlen("kill")) == 0)
        {
            char *target_pid = strtok(NULL, " \n");
            int childStatus;
            pid_t spawnPid = fork();
            switch (spawnPid)
            {
            case -1:
                perror("fork()\n");
                exit(1);
                break;
            case 0:
                // This is the child process where we will call the ls function
                kill_process(target_pid);
                perror("execv");
                exit(2);
                break;
            default:
                // This is the parent process that takes control back after child process finishes.
                spawnPid = waitpid(spawnPid, &childStatus, 0);
                printf("CHILD STATUS: %d\n", childStatus);
                processStatus = childStatus;
                break;
            }

Even after killing that sleep process, it still shows up when I check my current processes running with ps. Please see my screenshot below for the same execution.

~/Desktop/OSU/CS-344 (Operating Systems)/assignment3(main*) » ./a.out                                                               sampai@sams-mbp-2
: ps
  PID TTY           TIME CMD
25223 ttys003    0:06.24 /bin/zsh -l
41134 ttys003    0:00.00 ./a.out
32018 ttys004    0:01.49 -zsh
30707 ttys005    0:00.14 /bin/zsh --login -i
: sleep 30 &
background pid is 41143
: ps
  PID TTY           TIME CMD
25223 ttys003    0:06.24 /bin/zsh -l
41134 ttys003    0:00.00 ./a.out
41143 ttys003    0:00.00 sleep 30
32018 ttys004    0:01.49 -zsh
30707 ttys005    0:00.14 /bin/zsh --login -i
: kill 41143
CHILD STATUS: 0
: ps
  PID TTY           TIME CMD
25223 ttys003    0:06.24 /bin/zsh -l
41134 ttys003    0:00.00 ./a.out
41143 ttys003    0:00.00 (sleep)
32018 ttys004    0:01.49 -zsh
30707 ttys005    0:00.14 /bin/zsh --login -i
:

CodePudding user response：

Figured it out! Basically like kaylum said in the comments, I needed to add a waitpid call outside of my switch statement. And I needed to wait on the correct pid, which I needed to get inside of the child process. Please see my updated code below.

int process_pid;
            pid_t spawnPid = fork();
            switch (spawnPid)
            {
            case -1:
                perror("fork()\n");
                exit(1);
                break;
            case 0:
                // This is the child process where we will call the ls function
                process_pid = getpid();
                kill_process(target_pid);
                perror("execv");
                exit(2);
                break;
            default:
                // This is the parent process that takes control back after child process finishes.
                spawnPid = waitpid(process_pid, &childStatus, 0);
                processStatus = childStatus;
                break;
            }
            spawnPid = waitpid(process_pid, &childStatus, 0); // Need this to kill zombie process.
            printf("CHILD STATUS: %d\n", childStatus);

CodePudding user response：

try kill -9 <PID> it must work