[TBD]inotify: Linux way to monitor directory changes

Introduction

Laymen explanation

Technical explanation

The inotify API provides a mechanism for monitoring file system events. Inotify can be used to monitor individual files, or to monitor directories. When a directory is monitored, inotify will return events for the directory itself, and for files inside the directory.

Example code:

Refer https://github.com/krdpk17/python/blob/master/linux_inotify_test.c

code to watch a directory /home/strike/

#include <stdio.h> #include <stdlib.h> #include <errno.h> #include <sys/types.h> #include <sys/inotify.h> #define EVENT_SIZE ( sizeof (struct inotify_event) ) #define BUF_LEN ( 1024 * ( EVENT_SIZE + 16 ) ) int main( int argc, char **argv ) { int length, i = 0; int fd; int wd; char buffer[BUF_LEN]; fd = inotify_init(); if ( fd < 0 ) { perror( "inotify_init" ); } wd = inotify_add_watch( fd, "/home/strike", IN_MODIFY | IN_CREATE | IN_DELETE ); length = read( fd, buffer, BUF_LEN ); if ( length < 0 ) { perror( "read" ); } 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; } ( void ) inotify_rm_watch( fd, wd ); ( void ) close( fd ); exit( 0 ); }

Reference

https://www.ibm.com/developerworks/library/l-ubuntu-inotify/index.html

https://linux.die.net/man/2/inotify_add_watch