fstrlen.c

(plain text) 
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#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/wait.h>

int fstrlen (const char *p) {
  pid_t child = vfork();

  switch (child) {
  case -1:
    perror("fork() failed");
    exit(EXIT_FAILURE);

  case 0:
    exit(*p ? 1 + fstrlen(p + 1) : 0);

  default:
    {
      int status;
      waitpid(child, &status, 0);
      return WIFEXITED(status) ? WEXITSTATUS(status) : EXIT_FAILURE;
    }
  }
}

int main () {
  printf("%d\n", fstrlen("abcde"));
  return 0;
}