execl in C programming

Question

I have a C program. I noticed that you can't put 2 execl's in it.

The code:

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

int main()

{
      pid_t fork(void);

      int system(const char *command);

      execl("/bin/sh", "sh", "-c", "kdialog --warningcontinuecancel 
      \"Make sure to include: \n \n 1. py_lcd folder \n 2. 4x20 
      Raspberry Pi LCD Display \n 3. Python 2.7.12 to be installed \n 
      \n If you are missing something, kill the program process and 
      get them.\"", (char *) 0);

      sleep(1);

      execl("/bin/sh", "sh", "-c", "kdialog --msgbox \"Setting up files...\" --title \"Installing...\"", (char *) 0);
      return(0);
}

Can someone help me if there is a way to bypass this or if i am making a mistake???

Answer 1

The exec family of functions don't return when they succeed. They replace the running process with the one being execed. If you want to run a program in a child process (with full control, unlike system), you need to use fork + exec + wait (or perhaps posix_spawn).

Answer 2

Anything written after execl is a deadcode. The main purpose of execl is to re-use the current process information for a new process to improve performance. You will be using sharing the same structures of process information(pid, stack, heap etc.) of the current process where execl is executed.

Answer 3

I found an answer myself. There is a system() command which works the exact same but you are able to insert it anywhere in the code without problems