Summary - Process management

Combine fork, exec and wait to write a shell.

The shell pattern

In this group you learned the three core tools of process management: create a process with fork, replace the program with exec, and wait with wait. Together they form the basis of UNIX shells.

Now you will combine them into a simple shell: fork a child, run the command with execvp in the child, and wait in the parent. This pattern runs behind every command-line shell.

Exercise Mini shell

Create a child with pid_t pid = fork();. In the child, char *args[] = {"echo", "merhaba", NULL}; and execvp("echo", args);. In the parent, int status; wait(&status); and printf("bitti\n");.

Show example solution

#include <stdio.h>
#include <unistd.h>
#include <sys/wait.h>
#include <stdlib.h>

int main(void) {
    pid_t pid = fork();
    if (pid == 0) {
        char *args[] = {"echo", "merhaba", NULL};
        execvp("echo", args);
        _exit(1);
    }
    int status;
    wait(&status);
    printf("bitti\n");
    return 0;
}

Next steps

You learned process management. In the next groups you will see inter-process communication with signals, concurrent work with threads, and network communication with sockets.

All these topics build on fork, exec and wait. For example, a server uses fork to create a child for each client. getpid and exit will appear everywhere for debugging and clean exit.

Test yourself

What sequence does a shell follow to run a command?
- exec, fork, wait
- wait, fork, exec
- fork, wait, exec
- fork, exec, wait
Show answer

fork, exec, wait — First fork, then exec in child, then wait in parent.
Match the shell steps

fork

Create process
execvp

Run program
wait

Wait for child
exit

End process

Next lesson: What are signals?

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