Gofer

A slave that runs tasks on the basis of every file/directory change.

What does it do?

Simply put, it runs an executable (shell script, or a binary) every time a file's/directory's content changes.

How does it know something has changed?

It is based on inotify (on Linux), and FSEvents (on Mac), and uses the excellent fsnotify package under the hood.

What platforms does it run on?

It runs well on Linux (Ubuntu has been tested), and Mac. Haven't checked on Windows, but since fsnotify is a cross-platform library, there's no reason why it shouldn't run on Windows.

Show me how to run this thing!

Download the binary, or download the source code and build your own binary.
gofer {MENTION YOUR CONFIG FILE HERE}

How does the Config file look like?

A Gofer config file is a valid JSON file that consists of the following parameters:

[
	{
		"source" : "{{SourceJSON File location}}",
		"log" : "{{Log file where the output needs to be written}}"
	},
	{
		"source" : "{{SourceJSON File location}}",
		 "log" : "{{Log file where the output needs to be written}}"
	}
]

OK, but what's a SourceJSON file?

A SourceJSON file is another valid JSON file that consists of all the files and folders to monitor, as well as the scripts that are supposed to run when they change. The structure of each SourceJSON file is as follows:

{
	"loc" : [
		{
			"dir" : "{{Absolute Path name of the file or directory to 
			monitor}}",
			"exec" : "{{Absolute Path name of the executable that 
			needs to be run when a change has occurred}}",
			"path" : "absolute"
		},
		{
			"dir" : "{{Relative Path name of the file or directory 
			to monitor}}",
			"exec" : "{{Relative Path name of the executable that 
			needs to be run a change has occurred}}",
			"path" : "relative"
		}
	],
	"selfobserve" : bool
}

selfobserve is a boolean (true/false) flag that directs gofer to reload the SourceJSON file in case there's a change in it. This is so that another program could probably keep appending to the SourceJSON file, and Gofer would automatically adjust.

loc is an array that consists of the rules for a particular source file/directory (dir), an exec string that holds the path of the executable that is fired when there's a modification in dir, and a path parameter that mentions if the dir and the exec paths are relative or absolute. If path is relative, then the exec path is resolved relative to the dir path. If path is absolute, the exec path is resolved as the absolute path.

What's the difference between a Gofer Config file and a SourceJSON

file? A Gofer Config file consists of all INDEPENDENT SourceJSON files that need to be observed. It's kinda like configuring Nginx/Apache to serve multiple websites on the same server. It lends the flexibility of monitoring multiple SourceJSON files, thus making organization and maintenance a lot cleaner.

A SourceJSON file would consist of all the rules for a particular logical project.

Why would anyone need Gofer?

Gofer would make a developer's life easier, by running a particular script. For e.g., if a source file has changed, Gofer could be configured to create a new build immediately. Or, it could be configured to send a POST request whenever a directory has been modified. Or, if Gofer is monitoring a database (such as PostgreSQL), it can be configured to sync the WAL file with a remote server. The possibilities are endless.

Wouldn't it be using a lot of CPU cycles?

Not really. On Linux (the main targeted platform), it is based on inotify, and hence, is very light. Gofer would only run the exec script when there's a change. Will update this with more data once comprehensive tests have run.

What is the current version?

Gofer is currently pre-alpha. It would be safe to say that it isn't ready for production yet. But, it should fly when used for personal tasks.

mutohq/Gofer