watchman-make is a convenience tool to help automatically invoke a build tool or script in response to files changing. It is useful to automate building assets or running tests as you save files during development.

watchman-make will establish a watch on the files you specify and remain running in the foreground, waiting for changes to occur. When a change is triggered, your build tool or script will be run in the foreground with its output being passed through to your terminal session (or wherever you may have redirected it).

Events are consolidated and settled before they are dispatched to your build tool so that it won’t start executing until after the files have stopped changing. The --settle argument controls the settle duration.

watchman-make requires pywatchman (and thus requires python) as well as watchman.


$ watchman-make -p '**/*.c' '**/*.h' 'Makefile*' -t all -p 'tests/**/*.py' 'tests/**/*.c' -t integration
# Relative to /Users/wez/fb/watchman
# Changes to files matching **/*.c **/*.h Makefile* will execute `make all`
# Changes to files matching tests/**/*.py tests/**/*.c will execute `make integration`
# waiting for changes


You can tell watchman-make about one or more build targets and their dependencies, and it will then trigger the build for those targets as changes are detected.

The example above defines two targets using the -t argument; all and integration. These correspond to targets with the same names in the watchman Makefile. Each target will pick up the list of patterns defined by the -p argument that precedes it.

$ watchman-make -p '**/*.c' '**/*.h' -t all

The above defines a target named all that will be triggered whenever any combination of files are changed that have filenames that match either of the patterns *.c or *.h at any level in the directory tree (that’s what the ** portion means). When it triggers, watchman-make will execute make all.

If you don’t use make, you can use the --make option to tell watchman-make to use your builder of choice. When a target is triggered, watchman-make will concatenate the value of --make with the name of the target and execute that command using the shell.

The target name has no special meaning to watchman-make, it is used only to construct the command to invoke. There is no special logic or support that is specific to Makefiles or make.

Multiple Targets

There are two different ways to specify multiple targets. The first is shown in the main example at the top of this page and is repeated here:

$ watchman-make -p '*.c' '*.h' 'Makefile*' -t all -p 'tests/**/*.py' 'tests/**/*.c' -t integration

This defines two independent targets, all and integration that each have a list of patterns defined as their triggers. Each time you specify a target using the -t option, the value of the -p option is cleared.

The above will cause make all to be run if you change a file that matches .*c (at the top level of the tree), and will cause make integration to run if you change a source file under the tests directory.

An alternative is to list multiple target names with your -t option:

$ watchman-make -p '*.c' '*.h' 'Makefile*' 'tests/**/*.py' 'tests/**/*.c' -t all integration

this will execute make all integration if you change any top level *.c file or test source file.

Run Scripts

Since 4.8.

As an alternative to targets, you can provide the path to a script which watchman-make will execute when changes are detected.

$ watchman-make -p '**/*.c' '**/*.h' --run

The above will run the provided script whenever any combination of files are changed that have filenames that match either of the patterns *.c or *.h at any level in the directory tree. When it triggers, watchman-make will execute

You must run watchman-make with either --target or --run, but they cannot be run together