Length of an argv vector

Challenge

The exec family receives arguments as a NULL-terminated array of string pointers (argv). Count how many arguments it holds.

Task

Implement int argv_len(const char *const *argv) that returns the number of entries before the terminating NULL pointer.

Input

• argv: array of char *, terminated by a NULL pointer.

Output

The count of non-NULL entries.

Example

argv_len({"ls", "-l", "/tmp", NULL})   ->   3
argv_len({NULL})                       ->   0

Edge cases

• First entry is NULL: return 0.

Input format

argv: NULL-terminated array of string pointers.

Output format

Number of entries before the NULL terminator.

Constraints

The array is always NULL-terminated.

Starter code

#include <stddef.h>

int argv_len(const char *const *argv) {
    /* TODO */
    return 0;
}

Common mistakes

Creating zombie processes by failing to reap child with wait/waitpid; forgetting that code after successful execvp() is never reached.

Edge cases to handle

Fork failure (EAGAIN); child process crashing with signal; parent terminating before child; waitpid() with WNOHANG on running child.