execute_rest.c

#include"header.h"
#include"variables.h"

void proc_exit(int mysig)
{
    //int wstat;
    union wait wstat;
    pid_t   pid;

    while (1) {
        pid = wait3 (&wstat, WNOHANG, (struct rusage *)NULL );
        if (pid == 0){
            return;
        }
        else if (pid == -1){
            return;
        }
        else if (wstat.w_retcode == 0)
        {
            for(int i = 0;i < background_jobs; i++){
                if(job[i].pid == pid)
                    pop_job(i);
            }
            printf ("pid:%d Return code: %d\n",pid, wstat.w_retcode);
        }
    }
}

void proc_killed(){
    printf("function called\n");
    union wait wstat;
    pid_t   pid;

    while (1) {
        pid = wait3 (&wstat, WNOHANG, (struct rusage *)NULL );
        if (pid == 0){
            return;
        }
        else if (pid == -1){
            return;
        }
        else if (wstat.w_retcode == 0)
        {
            
            printf ("pid:%d Return code: %d\n",pid, wstat.w_retcode);
        }
        printf("killed\n");
    }
}

int execute_rest(char **args, int flag){
    int fd[2];
    pipe(fd);
    int i = 0, background = 0, status;
    while(args[i]){     // & can only be applied at last of the process
        i++;
    }
    signal (SIGTERM, proc_killed);
    signal (SIGCHLD, proc_exit);
    int ret = fork();
    if (ret == 0)
        exit(rand());
    else if (ret == -1)
    {
        perror("main: fork");
        exit(0);
    }
    else
        pause();
    if(string_compare(args[i-1], "&")){
        background = 1;
        args[i-1] = NULL;
    }
    
    #define CHECK(x) if(!(x)) { perror(#x " failed"); abort(); /* or whatever */ }
    /* Block SIGINT. */
/*    sigset_t mask, omask;
    sigemptyset(&mask);
    sigaddset(&mask, SIGINT);*/
    pid_t pid = fork();

    if(pid == 0){
        //if (background!=0)  setpgid(0, 0);   
        // means if it is the child process
        // Everything happens only here, after this gets executed, the dup2 are restored as earlier.
        if (file_in != 0)
        {
            dup2(file_in,0);
            close(file_in);
        }
        if (file_out != 1)
        {
            dup2(file_out,1);
            close(file_out);
        }
        if (flag)
        {
            dup2(fd[1],1);				// the command output is in fd[1], after this process exits, stdout remains 1 only
            close(fd[1]);				
        }
        if(execvp(args[0], args) == -1){
            fprintf(stderr, "%s: command not found\n", args[0]);
            exit(0);   // means stop this child process
        }
        exit(0);
    }   
    else if(pid > 0){   // this is the parent process

        if(background == 0){
            int status;
            child_pid.pid = pid;
            strcpy(child_pid.name, args[0]);
            strcpy(child_pid.status, "Stopped");
            child_pid.flag = 0;
            //wait(NULL);     // wait till we don't send signal to you or till your child hasn't exited
            //waitpid(-1, &status, WUNTRACED);    // This waits untill the child process changes it's state.
            waitpid(-1, &status, WCONTINUED | WUNTRACED);
        }
        else
        {
            //CHECK(sigprocmask(SIG_BLOCK, &mask, &omask) == 0);
            job[background_jobs].pid = pid;
            strcpy(job[background_jobs].status, "Running");
            strcpy(job[background_jobs].name, args[0]);
            job[background_jobs].flag = 1;
            background_jobs++;
            printf("[%d]\n", pid);
        }
        file_in = fd[0];            // Getting file_in , to use input for next command
        close(fd[1]);
    }
    else{
        fprintf(stderr, "%s: forking not done properly\n", args[0]);
    }
    return 1;
}