Minimal build system for maximal efficiency

build-if-changed is like a portable version of make but way more simple. given a bunch of file patterns it executes a command if (and only if) any of the files inside the patterns did change. A simple pattern that allows for powerful composition for dependent build tasks.

npm install -g build-if-changed

Run build-if-changed in any directory. It will search in the current directory or upwards for a file named buildconfig.

A build config file looks like this:

[some command]
out: glob pattern of files produces by this command
glob pattern1 to watch
glob pattern2 to watch

[another command]
more patterns to watch

build-if-changed will calculate the hashes of all files that match the glob patterns, and execute the corresponding command(s) if the files did change since the previous run of build-if-changed. It is perfectly fine if the output of one command is watched by another command, build-if-changed will keep trying to run commands until no files change anymore.

If one or more out: patterns are provided build-if-changed will also check the generate files to determine whether a command should run. This is useful if you for example delete or alter the produced files and want to make sure that build-if-changed also runs in these cases.

Glob patterns and patterns are always interpreted relatively to the location of the buildconfig file.

Also see the examples directory for some examples.

This is what using build-if-changed looks like:

Command syntax is: `build-if-changed [--watch] [-c directory] [--clean] [file1] [file2]

(TODO) Same as build-if-changed, but, as suggested, will keep watching the files for any future changes. The watch will continue to run even if some commands did fail.

(TODO) Run's build-if-changed in the specified directory, searching for a buildconfig file in that directory and upward.

(TODO) Reads configuration from the specified configuration file(s). Note that the configuration files are still interpreted relatively to their own location.

(TODO) Drops the .buildifchanged directory and thereby forcing all commands to run upon the next invocation of build-if-changed.

Q: What is this magically appearing .buildifchanged folder?

A:File hashes as stored in the folder .buildifchanged in the same directory as the buildconfig file. This file should be excluded from version control.

Q: Does the order of commands matter?

A: Yes. It doesn't matter for the buid result, but it does matter for performance. If command A produces input for command B, A should be defined before B. Otherwise the system might run the commands B, A, B instead of just A, B.

Q: Does it run on Windows?

A: Yes. But remember; only use forward, unix-style slashes in patterns to denote the path separator.

Q: Why can a build command be only one line?

A: Separation of concerns; build-if-changed only determines when your build tools should be run. Complex commands should be organized outside build-if-changed so that you can test, version and invoke them manually. Use any tool you are comfortable with to organize your build scripts, sh, npm, gulp, webpack....