Using system and popen

• The system and popen functions in the standard C library provides an easy way to execute a command from within a program, much as if the command had been typed into a shell.
• For lazy programmers, the system and popen functions exist. These functions must not be used in any security sensitive program.
• These functions fork and then exec the user's login shell that locates the command and parses its arguments.
• They use one of the wait family of functions to wait for the child process to terminate.
• The popen function is similar to system, except it also calls pipe and creates a pipe to the standard input or from the standard output of the program, but not both.

  #include <stdlib.h>
  
  int main ()
  {
    int return_value;
    return_value = system ("ls -l /");
    return return_value;
  }
  

• The system function returns the exit status of the shell command. If the shell itself cannot be run, system returns 127; if another error occurs, system returns -1.
• Because the system function uses a shell to invoke your command, it's subject to the features, limitations, and security flaws of the system's shell.