fswatch is a cross-platform, file change monitor that gets notification alerts when the contents of the specified files or directories are altered or modified.


It executes four types of monitors on different operating systems such as:

  • A monitor build on the File System Events API of Apple OS X.
  • A monitor based on kqueue, a notification interface present in FreeBSD 4.1 also supported on many *BSD systems, OS X inclusive.
  • A monitor based on File Events Notification API of the Solaris kernel plus its spin-offs.
  • A monitor based on inotify, a kernel subsystem that shows file system modifications to apps.
  • A monitor based on ReadDirectoryChangesW, a Windows API that records alters to a directory.
  • A monitor that regularly check that status of the file system, keeps file modification times in memory, and manually determine file system changes (which works anywhere, where stat can be used).


Features of fswatch:

  • Supports several OS-specific APIs
  • Allows recursive directory monitoring
  • Performs path filtering using including and excluding regular expressions
  • Supports customizable record format
  • Additionally, it supports periodic idle events


How To Install fswatch in Linux Systems


Unfortunately, fswatch package is not available to install from the default system repositories in any Linux distributions. The only way to install the latest version of fswatch is to build from source tarball as shown in the following installation instructions.


First, grab the latest fswatch tarball using the following wget command and install it as shown:

$ wget https://github.com/emcrisostomo/fswatch/releases/download/1.9.3/fswatch-1.9.3.tar.gz
$ tar -xvzf fswatch-1.9.3.tar.gz
$ cd fswatch-1.9.3
$ ./configure
$ make
$ sudo make install



Make sure you’ve GNU GCC (C and C++ Compiler) and Development Tools (build-essential on Debian/Ubuntu) installed on the system before you compile fswatch from the source. If not, install it using the following command on your respective Linux distributions..

# yum group install 'Development Tools'		[On CentOS/RHEL]
# dnf group install 'Development Tools'		[On Fedora 22+ Versions]
$ sudo apt-get install build-essential          [On Debian/Ubuntu Versions]


On Debian/Ubuntu distributions, you might get the following error while executing fswatch command..


fswatch: error while loading shared libraries: libfswatch.so.6: cannot open shared object file: No such file or directory


To fix it, you need to execute the command below, this will help refresh the links and cache to the dynamic libraries before you can start using fswatch.

$ sudo ldconfig


How do I use fswatch on Linux?


The general syntax for running fswatch is:

$ fswatch [option] [path]


On Linux, it is recommended that you use the default inotify monitor, you can list available monitors by employing the -M or - list-monitors option:

$ fswatch -M
$ fswatch --list-monitors


The command below enables you to watch the changes in the current directory (/home/rootadminz), with events being delivered to standard output every 4 seconds.


The -l or –-latency option allows you to set the latency in seconds, the default being 1 second.

$ fswatch -l 4 . 


The next command monitors changes to the /var/log/auth.log file every 5 seconds:

$ fswatch -l 5 /var/log/auth.log


Using -t or --timestamp option prints the time stamp for every event, to print the time in UTC format, employ -u or --utf-time option. You can as well format time using -f or --format-time format option:

$ fswatch --timestamp /var/log/auth.log


Next, -x or --event-flags tells fswatch to print the event flags alongside the event path. You can use –event-field-seperator option to print events using the particular separator.

$ fswatch --events-flags ~ /var/log/auth.log


To print the numeric value of an event indicating changes in your home directory and /var/log/auth.log file, use  -n or --numeric option as below:

$ fswatch --numeric ~ /var/log/auth.log 


Perhaps you can look through the fswatch man page for detailed usage options and information:

$ man fswatch


Was this answer helpful? 0 Users Found This Useful (0 Votes)