I need some help here. I need to execute all three execlp() once I run the program but what happen is that only case 0 is executed.I changed pid to 1 and case1 gets executed and so on. Tried putting it in a for loop but does not work. I changed break to continue but still the same - only one process is executed. Any suggestions?
main(){
pid_t pid;
pid= fork();
int i;
if(pid==0){
for (i=0; i<3; i++){
switch (i){
case 0:
execlp("/bin/cat", "cat", "wctrial.txt", NULL);
break;
case 1:
execlp("/bin/mkdir", "mkdir", "mydirectory", NULL);
break;
case 2:
execlp("/bin/wc", "wctrial.txt", NULL);
break;
}
}
}else{
wait(NULL);
printf("Child process completed!");
exit(0);
}
}
According to man execlp
:
The
exec()
family of functions replaces the current process image with a new process image.
(emphasis is mine)
Therefore, once you called successfully execlp
, the process doesn't re-execute the old code.
case 0:
execlp("/bin/cat", "cat", "wctrial.txt", NULL);
/* shouldn't go here */
break;
If you want to execute the three programs, you can create three processes. For instance (loops unrolled):
pid_t son;
son = fork();
if (son == -1) /* report */
else if (son == 0) execlp("/bin/cat", "cat", "wctrial.txt", NULL);
else wait(NULL);
son = fork();
if (son == -1) /* report */
else if (son == 0) execlp("/bin/mkdir", "mkdir", "mydirectory", NULL);
else wait(NULL);
/* ... */
See also Kirilenko's answer. The solution is to use system(..)
instead of execlp(..)
.
Man page here .
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