This is the sample program to notify us when the file /tmp/myinput is modified

filewatch.c

/*This is the sample program to notify us when the file /tmp/myinput is modified */
#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <sys/types.h>
#include <linux/inotify.h>

#define EVENT_SIZE  ( sizeof (struct inotify_event) )
#define EVENT_BUF_LEN     ( 1024 * ( EVENT_SIZE + 16 ) )

int main() {
    int length;
    int fd;
    int wd;
    char buffer[EVENT_BUF_LEN];

    /*creating the INOTIFY instance*/
    fd = inotify_init();

    /*checking for error*/
    if ( fd < 0 ) {
        perror( "inotify_init" );
    }

    /*adding the “/tmp” directory into watch list. Here, the suggestion is to validate the existence of the directory before adding into monitoring list.*/
    wd = inotify_add_watch( fd, "/tmp/myinput", IN_MODIFY );

    while(1){
        int i=0;
        /*read to determine the event change happens on “/tmp” directory. Actually this read blocks until the change event occurs*/
        length = read( fd, buffer, EVENT_BUF_LEN );
        printf("got something\n");

        /*checking for error*/
        if ( length < 0 ) {
            perror( "read" );
        }
        printf("length=%d\n",length);

        /*actually read return the list of change events happens. Here, read the change event one by one and process it accordingly.*/
        while ( i < length ) {
            struct inotify_event *event = ( struct inotify_event * ) &buffer[ i ];
            printf( "File s modified.\n");
            i += EVENT_SIZE + event->len;
        }
    }

    /*removing the “/tmp” directory from the watch list.*/
    inotify_rm_watch( fd, wd );

    /*closing the INOTIFY instance*/
    close( fd );
}