Hooking events using Inotify in C

#include<stdio.h>
#include<sys/inotify.h>
#include<unistd.h>
#include<stdlib.h>
#include<signal.h>
#include<fcntl.h> // library for fcntl function

#define MAX_EVENTS 1024  /* Maximum number of events to process*/
#define LEN_NAME 16  /* Assuming that the length of the filename
won't exceed 16 bytes*/
#define EVENT_SIZE  ( sizeof (struct inotify_event) ) /*size of one event*/
#define BUF_LEN     ( MAX_EVENTS * ( EVENT_SIZE + LEN_NAME ))
/*buffer to store the data of events*/

int fd,wd;

void sig_handler(int sig){

       /* Step 5. Remove the watch descriptor and close the inotify instance*/
       inotify_rm_watch( fd, wd );
       close( fd );
       exit( 0 );

}


int main(int argc, char **argv){


       char *path_to_be_watched;
       signal(SIGINT,sig_handler);

       path_to_be_watched = argv[1];

       /* Step 1. Initialize inotify */
       fd = inotify_init();


       if (fcntl(fd, F_SETFL, O_NONBLOCK) < 0)  // error checking for fcntl
       exit(2);

       /* Step 2. Add Watch */
       wd = inotify_add_watch(fd,path_to_be_watched,IN_MODIFY | IN_CREATE | IN_DELETE);

       if(wd==-1){
               printf("Could not watch : %s\n",path_to_be_watched);
       }
       else{
              printf("Watching : %s\n",path_to_be_watched);
       }


       while(1){

              int i=0,length;
              char buffer[BUF_LEN];

              /* Step 3. Read buffer*/
              length = read(fd,buffer,BUF_LEN);

              /* Step 4. Process the events which has occurred */
              while(i<length){

                struct inotify_event *event = (struct inotify_event *) &buffer[i];

                  if(event->len){
                   if ( event->mask & IN_CREATE ) {
                   if ( event->mask & IN_ISDIR ) {
                     printf( "The directory %s was created.\n", event->name );
                     }
                     else {
                       printf( "The file %s was created.\n", event->name );
                    }
                    }
                    else if ( event->mask & IN_DELETE ) {
                    if ( event->mask & IN_ISDIR ) {
                      printf( "The directory %s was deleted.\n", event->name );
                    }
                    else {
                      printf( "The file %s was deleted.\n", event->name );
                    }
                    }
                    else if ( event->mask & IN_MODIFY ) {
                    if ( event->mask & IN_ISDIR ) {
                      printf( "The directory %s was modified.\n", event->name );
                    }
                    else {
                     printf( "The file %s was modified.\n", event->name );
                    }
                    }
                   }
                   i += EVENT_SIZE + event->len;
          }
    }
}

References

How to Use inotify API in C Language – Linux Hint