Fork and Wait

Task

Implement fork_and_run function

• Fork a child process
  • Child: Execute the given command using execlp
  • Parent: wait for the child to complete
• The function takes a command and a single argument
• If fork fails, call perror("fork") and return -1
• If exec fails in the child, call perror("exec") and exit(1)
• The parent should wait for the child and return 0 on success

Important System Calls

• fork() → creates a child process, returns 0 in child, child PID in parent, -1 on error
• execlp(command, command, arg, (char*)NULL) → replaces process with command
• wait(NULL) or waitpid() → parent waits for child

Function Signature

// Fork a child process. Child runs command with arg using execlp.
// Parent waits for child. Return 0 on success, -1 on error.
int fork_and_run(const char* command, const char* arg);

---

Example

$ gcc fork_and_wait.c -o fork_and_wait
$ ./fork_and_wait
ls -l
total 16
-rwxr-xr-x 1 user user 16704 Nov  6 10:00 fork_and_wait
-rw-r--r-- 1 user user  1234 Nov  6 10:00 fork_and_wait.c
Parent: child completed
$ ./fork_and_wait
echo hello
hello
Parent: child completed

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Code

#include <sys/wait.h>
#include <unistd.h>
 
int fork_and_run(const char* command, const char* arg) {
    int pid = fork();
    if (pid < 0){
        perror("fork");
        return -1;
    } else if (pid == 0){
        execlp(command, command, arg, (char*)NULL);
        perror("exec");
        exit(1);
    } else {
        waitpid(pid, NULL, 0);
        return 0;
    }
}