A tiny tool that watches for file changes and executes a command when it happens

Because it's a need that keeps coming up. Whether you want to implement your own SASS/LESS precompiler, or just want to reload your localhost page when you change something, even if you just want to keep a second copy of any set of documents - this little guy is there for you.

It just does what most similar tools do: polls the filesystem. Thanks to caching and the growing market share of SSDs, today you literally won't feel a thing even if it's a few hundred files - but it rarely will be, I guess. You can fine tune this tool to the actual file patterns that are likely to change, and there you go.

• Multiple file patterns are supported
• You can give it a little rest between the polls
• You can specify a settledown time after changes

When a file changes, it's rarely a good idea to do something right away; maybe it is, you decide, but it's very efficient to only react on changes when they're settled, that is, a few seconds passed since the save button. If you don't use this option, reaction will be almost immediate - depending on the wait option, but as soon as the file is changed, action will follow.

The simplest thing to do is make a short beep when a file changes:

d:\projects\demo1> onfileschanged beep.bat *.css *.js *.php --new-process

Now in projects/demo1, whenever a php/js/css file changes, beep.bat will be launched in a new process, and since it's nothing but a chr(7) and an exit, the command window will only briefly flash up, then disappear again; but you'll hear the beep.

Here's an example that makes a bit more sense:

d:\projects\demo1> onfileschanged less-compiler.bat *.less

Now every time you change any of your .less files, that little batch of yours will be launched (hopefully you have a .less compiler and you know how to run it from a batch), so you don't have to do it manually. Even better, if you do it like this:

d:\projects\demo1> onfileschanged less-compiler.bat *.less --settledown 10

This time, whenever a change happens, onfileschanged will count down from 10 and only launch the command if there are no further changes in this time period. If you're like me, hitting Save quite often during work, your CPU will thank you for not having to work every time.

Just run the program from command line with no arguments.

D:\>onfileschanged

    onFilesChanged                                    (c) 2019, Denes Kellner
    --------------

    Watches one or more file patterns (mydir/*.xxx) for changes, and executes
    a certain command when it happens. Optionally you can wait for a while to
    avoid too frequent reactions - this is called a settledown time, it means
    that after a change, there should be n seconds of non-changing to trigger
    the action. A very handy tool for continuous backups.

    Syntax:

        onfileschanged <command> <pattern1> <pattern2>
        onfileschanged <command> -l <listfile>
        onfileschanged quit -l <listfile>

    Options:

        -l, --listfile          A textfile with list of patterns to watch
                                (one pattern per line, no magic)
        -i, --idletext          Text to display in taskbar when watching
        -a, --actiontext        Text to display when dealing with changes
        -c, --countdowntext     Text to display when waiting for settledown
        -w, --wait              Wait n seconds between polls
        -n, --new-process       Open a new process when reacting on changes
                                (useful when you don't want to wait till it
                                finishes)
        -s, --settledown        Act only when something has changed but then
                                things settled down for n seconds. (Good for
                                delayed action on a quick series of changes)


D:\>