psmay's take on .bashrc.d

I'm not the first person to splay the commands of my .bashrc into a number of other files to be auto-read from a ~/.bashrc.d/ directory, and I won't be the last.

Features

The defining features of my version are these:

• Initially, the only scripts to be included are those whose names do not match __*, .*, or *.*.
  • For example, a script named startfoo would be run by default, but a script named startfoo.sh would not.
• Scripts can specify dependencies by saying #require at the beginning of a line and following it with a space-delimited list of other script filenames.
  • A script can require a file that was initially excluded. If a script named startfoo contains a line #require startfoo.sh, then startfoo.sh will be scheduled to be sourced (even though it would otherwise have been excluded) before startfoo is sourced.
  • A script can require a file that would already have been included. If a script named startfoo contains a line #require zotfoo, then zotfoo will be sourced before startfoo.
• Ordering is derived only from dependencies. If a script must wait until after another script has been included, specifying a dependency is the only way to ensure that they run in the correct order.
  • Any two scripts whose dependencies have already been met can be run in either order, and theoretically the order may change from run to run.
  • The scheduling does not fall back to alphabetical/lexicographical order.
  • The scheduling does not fall back to the order in which dependencies were required.
    • The require line #require foo bar is exactly equivalent to #require bar foo.

How to use

Create a ~/.bashrc.d/ directory. Populate it with a checkout of this repo (or, even better, a fork of this repo). The only especially critical file to include is __all; that is the script that sources other scripts.

Split your existing .bashrc into discrete task scripts and place each in a separate file under ~/.bashrc.d/. Omit any whitespace, periods, or leading __ in the filenames.

Move your existing .bashrc to another place for your future reference.

Create a new .bashrc:

# Instead of editing this file, consider adding/editing a script in
# ~/.bashrc.d/.
. ~/.bashrc.d/__all

That's it!

Dependencies

The #require mechanism is designed to take care of these problems:

• Ordering: There is no need to name task scripts to force a sort order. By specifying dependencies, a workable order can be determined automatically without altering filenames.
• Include-once: If there is a script that is needed by more than one other script (for example, one that contains function definitions and variables), using a dependency in each, instead of sourcing the script directly, helps prevent the script from being run redundantly.

If any of the task scripts must be preceded by another specify a dependency. For example, if early must be run earlier than late, add the following line to late:

#require early

(No whitespace may appear before #require.)

Circular dependencies

If some script (requires another script which)+ in turn requires the first script, the scheduling logic will croak citing a dependency loop.

This isn't something we can automatically fix—ultimately one script has to be sourced first. Analyze your scripts to determine whether one of the scripts really must precede another. It may be possible to separate one of the scripts into two parts in which only one has the dependency while the other satisfies the other script's dependency.

The idea is documented much better elsewhere.

Inseparable scripts

If a script must run immediately before another script, dependencies may not help.

Say we have three scripts, early, normal, and late, and late depends on early, but early and normal have no dependencies. The following are all valid orderings:

• early, normal, late
• early, late, normal
• normal, early, late

One of the possibilities is for normal to run between early and late. Most often this isn't an issue.

If early must be run immediately before late, it's probable that they should be combined into a single task. One way to do this is to concatenate early and late into early-late. If there are other scripts with dependencies on early or late, they should be changed into dependencies on early-late. After that change, the only valid orderings are

• early-late, normal
• normal, early-late

And this works.

License

The OSI-approved version of the MIT License (below) applies to this document and all scripts in this repository, insofar as they are substantial enough to protect under copyright.

Copyright © 2014 Peter S. May

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.