Invoking user space applications from the kernel

User-space applications are, most of the time, called from within the user space by other applications. Without going deep into the details, let's see an example:

#include <linux/init.h> 
#include <linux/module.h> 
#include <linux/workqueue.h>    /* for work queue */ 
#include <linux/kmod.h> 
 
static struct delayed_work initiate_shutdown_work; 
static void delayed_shutdown( void ) 
{ 
   char *cmd = "/sbin/shutdown"; 
   char *argv[] = { 
         cmd, 
         "-h", 
         "now", 
         NULL, 
   }; 
   char *envp[] = { 
         "HOME=/", 
         "PATH=/sbin:/bin:/usr/sbin:/usr/bin", 
         NULL, 
   }; 
 
   call_usermodehelper(cmd, argv, envp, 0); 
} 
  
static int __init my_shutdown_init( void ) 
{ 
    schedule_delayed_work(&delayed_shutdown...