/**
* Start a process
* @return: PcbPtr of process / NULL if start failed
*/
PcbPtr startPcb(PcbPtr ps) {
pid_t pid;
/* if the process is suspended, restart */
if(ps->status == PCB_SUSPENDED) {
if (kill(ps->pid, SIGCONT)) {
fprintf(stderr, "Restart failed\n");
return NULL;
}
ps->status = PCB_RUNNING;
return ps;
}
/* otherwise, start Pcb */
switch(pid = fork()) {
case -1:
fprintf(stderr, "Starting failed\n");
return NULL;
break;
case 0: // in child(new) process
ps->pid = getpid();
ps->status = PCB_RUNNING;
printPcb(ps);
execvp(ps->args[0], ps->args);
break;
default: // in parent
ps->pid = pid;
kill(ps->pid, SIGCONT);
ps->status = PCB_RUNNING;
break;
}
return ps;
}
/*******************************************************
* PcbPtr startPcb(PcbPtr process) - start (or restart)
* a process
* returns:
* PcbPtr of process
* NULL if start (restart) failed
******************************************************/
PcbPtr startPcb (PcbPtr p)
{
if (p->pid == 0) { // not yet started
switch (p->pid = fork ()) { // so start it
case -1:
perror ("startPcb");
exit(1);
case 0: // child
p->pid = getpid();
p->status = PCB_RUNNING;
printPcbHdr(stdout); // printout in child to
printPcb(p, stdout); // sync with o/p
fflush(stdout);
execvp (p->args[0], p->args);
perror (p->args[0]);
exit (2);
} // parent
} else { // already started & suspended so continue
kill (p->pid, SIGCONT);
}
p->status = PCB_RUNNING;
return p;
}