soveran / prep

Read from stdin and prepend a string to each line while preserving identation.

prep

Read from stdin and prepend a string to each line while preserving identation.

prep is a tool for prefixing blocks of text. It reads from stdin, detects the indentation of the first line and proceeds to prepend the passed prefix to each line. If the prefix argument is omited it defaults to #. Lines containing only white space are preserved.

Installation

Download the latest release or check the available packages. You can also compile the source code in the master branch.

Install prep into /usr/local/bin with the following command:

$ make install

You can use make PREFIX=/some/other/directory install if you wish to use a different destination. If you want to remove prep from your system, use make uninstall.

Examples

$ cat foo.cr
  def foo
    puts "foo"
  end

$ cat foo.cr | prep
  # def foo
  #   puts "foo"
  # end

$ cat foo.cr | prep --
  -- def foo
  --   puts "foo"
  -- end

If you use vis, you can select a block of text and run this command:

:|prep

You can also pass a string to use for the comment:

:|prep --

Usage is similar with vim:

:'<,'>!prep

As vim gives a special meaning to some characters, you may have to escape them:

:'<,'>!prep \e%

Motivation

Most text editors provide the means for creating plugins that comment out text selections. That means tools similar to prep exist written in Lua, VimL, Emacs Lisp, etc. As it's often the case, once a person chooses a text editor they will stick to it for a long time, so once they have found a suitable plugin for commenting code there's no need to look for alternatives.

In my case, I switched from vim to vis, and like many other editors with vis I can replace some text range with the result of piping it to an external tool. The scripting language for vis is Lua, so I could have written this tool as a plugin. Instead, I thought about creating a specialized tool that can eventually be used from other editors or even from scripts. Also, even though we call the feature "commenting", it's just prepending a string while preserving the indentation. That means it has potential to cover other use cases.

Contributing

If you find a bug, please create an issue detailing the ways to reproduce it. If you have a suggestion, create an issue detailing the use case.