Gestion de processus

Bonjour,
- svl dit moi que fait ce program
#include<stdio.h>
#include<stdlib.h>
#include<sys/types.h>
#include<unistd.h>
int spawn (char* program, char** arg_list)
{pid_t child_pid;
child_pid=fork();
if (child_pid !=0)
return child_pid;
else { execvp (program, arg_list);
fprintf (stderr, "une erreur est survenue au sein de execvp\n");
abort ();
}
}
int main ()
{char* arg_list[] ={
"ls",
"-l",
"/",
NULL
};
spawn ("ls", arg_list);
printf ("fin du programme principal\n");
return 0;
}

- Et que fait exactement ces instriction:
int spawn (char* program, char** arg_list)
execvp (program, arg_list)
spawn ("ls", arg_list)