Spy is a compact file system watcher for Mac OS X and Linux (Note: Should work on Windows but is currently untested).


Spy expects a single argument, the directory or a single file to watch. Spy currently supports two different modes: watch and run mode. Press CTRL-D to stop watching for file system changes.

Watch mode

In output mode Spy will print the path to a modified file to STDOUT (followed by a newline) whenever a file modification (new file added, file modified, file deleted) occurs.

$> spy watch .

Because watch is the default mode you can omit the watch command if you want:

$> spy .

It's possible to watch a single file (this obviously only shows changes to that particular file):

$> spy /path/to/file

The default format is the full path to the modified file followed by a newline. To make it easier to parse the output, the --format=json changes the output to be printed formatted as a JSON object (again followed by a newline).

$> spy watch --format=json .
{"path":"/path/to/modified.file","flag":"Added","time":"2012-12-20 11:26:56.859456 UTC"}

Flag is one of "Added", "Modified", "Removed".

For directories the following options apply:

An optional second argument can be used to filter the files in the given directory using a glob pattern:

$> spy watch /path/to/directory "*.md"

Run mode

In run mode Spy will execute a given command whenever a file modification occurs without printing modifications to stdout. The command will be executed with the path to the modified file as the last argument.

$> spy run "./run-build.sh"

In the example above the shell script run-build.sh would be executed with the path to the modified file as the first argument.

If the command to be executed does not expect any (additional) arguments the --notify-only flag can be used. This will cause spy to execute the command without passing the path as an argument:

$> spy run --notify-only "rake test" .

To compile Spy for example use:

$> spy run -n "cabal build" src


Binary distribution

The binary distribution contains a 64bit binary compiled for Mac OS X or Linux.

Download the tarball from https://bitbucket.org/ssaasen/spy/downloads and run "make install" to copy the binary and the man page into the correct target directories:

$> curl -OL https://bitbucket.org/ssaasen/spy/downloads/spy-PLATFORM-ARCH-VERSION.tar.gz
$> tar xfz spy-PLATFORM-ARCH-VERSION.tar.gz
$> cd spy
$> make install

The user manual should now be available via man spy and the spy executable should be on your $PATH.

Homebrew on Mac OS X?

You can use:

brew tap juretta/spy
brew install spy

To install the latest spy release.

Source distribution

You need the Haskell platform installed and cabal-install available on your $PATH.

To install spy from hackage simply run:

$> cabal install spy


To install spy from git you need the Haskell platform installed and cabal-install available on your $PATH:

$> git@bitbucket.org:ssaasen/spy.git
$> cd spy
$> cabal install --only-dependencies
$> cabal configure
$> cabal build

This will create the spy binary in the ./dist/build/spy directory.

To copy the spy binary to the cabal bin directory (which should be available on your PATH) use:

$> cabal copy
Tip: Use camelCasing e.g. ProjME to search for ProjectModifiedEvent.java.