background.c

#include "headers.h"

// function to handle exit of background processes
void bg_handler(int sig)										
{
	int status;
    pid_t pid = waitpid(-1, &status, WNOHANG);												// checking for zombie child process
    if(pid > 0)
    {
        char cmd[MX_L1]; 
		int chk = 0;
        for(int i = 0; i < num_job; i++)													// if exited process found, other processes after it
        {																					// are shifted left by one and thus the process is deleted from the array
            if(bg_jobs[i].pid == pid)
            {
				strcpy(cmd, bg_jobs[i].name);
                for(int j = i; j < num_job - 1; j++)
     			{
          			strcpy(bg_jobs[j].name, bg_jobs[j+1].name);
          			bg_jobs[j].pid = bg_jobs[j+1].pid;
     			}
     			num_job--;
                chk = 1;      
                break;
            }
        }
		if(chk && WIFEXITED(status) && WEXITSTATUS(status) == 0)							// process exited normally
        	fprintf(stderr, DFLT "\n%s with PID %d exited normally\n:')", cmd, pid);
        else if(chk)
        { 
			fprintf(stderr, DFLT "\n%s with PID %d failed to exit normally\n:'(", cmd, pid);
        }
        if(chk) 
			prompt();
        fflush(stdout);
	}
    return;
}

// function to initiate background process
void back(char **token)
{
    pid_t pid = fork();
	
    if (pid < 0)
    {
        perror(DFLT "fork error");
        strcpy(emoji,":'(");
    }
    else if (pid == 0)
    {
		setpgid(0, 0);
        int check = execvp(token[0], token);												// running the command in a new child process
        if (check < 0)
		{
            perror(DFLT "exec error");
            strcpy(emoji,":'(");
		}
		exit(0);
    }
    else
    {
        bg_jobs[num_job].pid = pid;															// storing name of last background process
        strcpy(bg_jobs[num_job].name, token[0]);											// storing job no. of last background process
		num_job++;
		printf(DFLT "[%lld] %d %s\n", num_job, pid, token[0]);
    }
	return;
}