Thread: Problem execl()

Hello everyone,

I am facing a problem with this code. Actually my program should create a new Shell that takes the hole path to a bin command (/bin/ls , /bin/date ...) so it can execute it by using the function execl()

I succeeded in creating the new Shell that works great but I still have a problem with using execl()

Here's my code :

Code:

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

int main() {
  int pid, longueur;
  char tab[TABSIZE], *s;
  int r;

  for (;;) {
    fputs("small_shell...> ", stdout);  
    s = fgets(tab, TABSIZE, stdin);

    if (s == NULL) {
      fprintf(stderr, "End Shell\n");
      exit(EXIT_SUCCESS);
    }
    longueur = strlen(s);
    tab[longueur - 1] = '\0';

    pid = fork();

    switch (pid) {
      case -1:
        break;
      case 0:
        r = execl(tab, (char*) NULL);
        if (r==-1) {          
          fprintf(stderr, "Error in exec\n");
        }
      default: 
        wait(NULL);
    }
  }
}

when I write /bin/date in the "small shell" for example, it tells me that "A NULL argv[0] was passed through an exec system call."

Does anyone has an idea how to solve this ?

Originally Posted by Salem

It should be
r = execl(tab, tab, (char*) NULL);

The first param is the path to the command you want to execute.
The second param is what will become argv[0], which by convention is the path to the program being run.

thank u Salem, it worked