Authored: 15 March 2018

Bash Shell Tweaks & Tips

Bash is the most common Unix shell. Bash is highly ubiquitous due to it being the default user shell for various flavours of Unix including: Linux, macOS and the Windows Subsystem for Linux (WSL).

Due to this ubiquity, and the need to maintain backward compatibility, it is rare that newer features of Bash are enabled by default. Some mistake this lack of default change for stagnation and simply move across to a different shell such as Zsh or Fish for their productivity enhancements.

This post will document a number of simple tweaks and tips, gleamed from the interwebs, that will improve user productivity when using Bash. A special note should be given to the Sensible Bash project for providing a couple noteworthy tips.

Many tweaks n’ tips noted in this post are baked into my bashrc and inputrc files.

macOS, upgrade to Bash 4.x

macOS by default ships with a very old version of Bash, version 3.2, due to licensing reasons. That version is over a decade old with many missing features.

Please upgrade to version 4.x of Bash. This is most easily accomplished by using the Homebrew package manager.

Install Homebrew followed by:

brew install bash

sudo su -
echo /usr/local/bin/bash >> /etc/shells
exit # Back to the user account

chsh -s /usr/local/bin/bash

Launch a new shell and enter echo $SHELL, it should list /usr/local/bin/bash.

bash-completion

Out of the box Bash only provides rudimentary filesystem based completions unlike the Zsh and Fish shells which offer command-aware completions. For example, shopt cd<TAB> should command-aware complete with the options of cdable_vars or cdspell as compared to completing with filenames or directories starting with cd (which is what standard Bash will do).

The bash-completion packages extends the Bash shell with intelligent completions for many common commands.

Most Linux distributions install and enable bash-completion these days.

Homebrew based Bash on macOS on the other hand will require bash-completion installation and invocation.

First install bash-completion:

brew install bash-completion

Then source bash-completion in your ~/.bashrc file:

. $(brew --prefix)/etc/bash_completion

Confirm that bash-completion is enabled by trying the shopt cd<TAB> example noted above, the aim is to have the cdable_vars and cdspell options displayed.

If you have never used command-aware completion before it will be a revelation how useful this capability is especially for commands such as git and ssh. Basically you want to hit the TAB key early and often.

Readline Configuration

The GNU Readline library is used by Bash, and certain other utilities, for line-editing and history management.

This library is configured by an .inputrc file in a user’s home directory. A list of recommended ~/.inputrc settings follows.

The TAB key cycles forward through the completion choices. Press an arrow key, such as right-arrow, to choose a selection.
```
  TAB: menu-complete
```
The Shift-TAB key cycles backward through the completion choices. This is useful if you pressed TAB too many times and overshot the desired choice. Like TAB, press an arrow key, such as right-arrow, to choose a selection.
```
  "\e[Z": menu-complete-backward
```
The first press of the completion key, TAB, will display a list of choices that match the given prefix, whilst the next press of the completion key will start cycling through the available choices.
```
  set menu-complete-display-prefix on
```
The above listed completion settings will result in Zsh AUTO_MENU-like completion behaviour.
Display completion matches upon the first press of the TAB key.
```
  set show-all-if-ambiguous on
```
Enable colors when completing filenames and directories.
```
  set colored-stats on
```
Filename and directory colors are defined in the LS_COLORS environment variable.
When a completion matches multiple items highlight the common matching prefix in color.
```
  set colored-completion-prefix on
```
The prefix color used will be the so option defined in the LS_COLORS environment variable.

Note, this is a new option only available with the latest versions of Readline (version 7.0 and above) and Bash (version 4.4 and above).
Ignore case when completing.
```
  set completion-ignore-case on
```
Treat hypens and underscores as equivalent when completing.
```
  set completion-map-case on
```
Automatically append the / slash character to the end of symlinked directories when completing.
```
  set mark-symlinked-directories on
```
Enable incremental history navigation with the UP and DOWN arrow keys. This will use the already typed text as a required prefix when navigating through history.
```
  "\e[A": history-search-backward
  "\e[B": history-search-forward
```

Disable beeps and do not display control characters.

  set bell-style none
  set echo-control-characters off

Readline Shortcuts

The Readline library also provides a number of useful default shortcuts.

Go to the beginning of the current line.
```
  Control-a
```
Go to the end of the current line.
```
  Control-e
```
Go back one word on the current line.
```
  Alt-b
```
Go forward one word on the current line.
```
  Alt-f
```
Search back through history.
```
  Control-r
```
This does a reverse search through history, from most recent to oldest, for commands that contain the chosen text. Hitting Control-r again cycles back through the matches whilst Control-Shift-r cycles forward.

In my case I have also mapped Control-f (f for find) in my ~/.inputrc to do the same searching.
```
  "\C-f": reverse-search-history
```
Append the last argument of the previous command to the end of the current command.
```
  Alt-.
```
For example, after doing mkdir some-long-directory simply enter cd <Alt-.> to add in the some-long-directory component to the end of the cd command.

Bash Settings

A more productive Bash experience is achieved by enabling and using the newer features the shell has made available.

The Bash shell is configured through a .bashrc file in a user’s home directory. A list of recommended ~/.bashrc tweaks follows.

Typing a directory name just by itself will automatically change into that directory.
```
  shopt -s autocd
```
Automatically fix directory name typos when changing directory.
```
  shopt -s cdspell
```
Automatically expand directory globs and fix directory name typos whilst completing. Note, this works in conjuction with the cdspell option listed above.
```
  shopt -s direxpand dirspell
```
Enable the ** globstar recursive pattern in file and directory expansions.
```
  shopt -s globstar
```
For example, ls **/*.txt will list all text files in the current directory hierarchy.
History settings.
```
  HISTCONTROL='erasedups:ignoreboth'
  HISTIGNORE=?:??
  HISTFILESIZE=9999
  HISTSIZE=9999
  PROMPT_COMMAND='history -a'
  shopt -s histappend
```
The Readline incremental and reverse search commands are much more useful when a good amount of history is kept. Note, we will also ignore all commands that are only one or two characters long.

Display Git branch details in the prompt.

  if [ -f $(brew --prefix)/etc/bash_completion.d/git-prompt.sh ]; then
      . $(brew --prefix)/etc/bash_completion.d/git-prompt.sh
  else
      . /etc/bash_completion.d/git-prompt
  fi
  GIT_PS1_SHOWUPSTREAM="auto"
  PS1="\h\$(__git_ps1) \w > "

Note, this is only a rudimentary prompt configuration, usually you will want to pretty it up with colors. Refer to to the prompt() function in my bashrc for a colored prompt example.

Automatically shorten deep paths in the prompt. The \w option in PS1 controls whether to display the path or not.
```
  PROMPT_DIRTRIM=4
```
Choose a smaller number if you wish to display less path components.
Enable history expansion with the SPACE key.
```
  bind Space:magic-space
```
For example, !!<SPACE> will immediately expand to the last command.

Bash Aliases

A Bash alias is a user defined shortcut. Aliases save keystrokes. Do not be afraid to alias long commands with shorter aliases, they will save you time.

As a starting point, here are some of the aliases from my ~/.bashrc file.

List command.

  alias ls='ls --color --classify --human-readable'
  alias ll='ls -l'
  alias ll.='ls -la'
  alias lls='ls -la --sort=size'
  alias llt='ls -la --sort=time'

We want colorization with human-readable file sizes. The last two aliases will order by size (largest to smallest) or by time (newest to oldest).

Easy navigation up a directory hierarchy.

  alias ..='cd ..'
  alias ..2='..; ..'
  alias ..3='..2; ..'
  alias ..4='..3; ..'
  alias ..5='..4; ..'

No more need to type cd ../../.., just do ..3 instead.

Git command.

  alias g=git
  complete -o default -o nospace -F _git g

If you use git, then why not save a couple characters?

Confirm unsafe file operations.
```
  alias cp='/bin/cp -i'
  alias mv='/bin/mv -i'
  alias rm='/bin/rm -i'
```
This will prompt to confirm when copying over, moving over or deleting a file.
List all files larger than a given size.
```
  alias llfs='find_by_size(){ find . -type f -size "$1" -exec ls --color --classify --human-readable -l {} \; ; }; find_by_size'
```
For example, llfs +10k will find and display all files larger than 10 kilobytes in the currect directory hierarchy.

There are a number of ways to navigate a file system: plain cd, pushd/popd, or defining a CDPATH environment variable as a short-circuit base directory.

The z utility provides a quicker way to change to an already visited directory. The z utility, which works in both Bash and Zsh, tracks the directories you visit with the cd command. Once trained you can just use the z command with a portion of a path to jump to a visited directory.

The z utility is most easily installed with Homebrew or Linuxbrew:

brew install z

Install the old fashioned way if you are not a Brew user.

Then source the z.sh file in your ~/.bashrc file:

. $(brew --prefix)/etc/profile.d/z.sh

Usage

First you need to train z:

cd ~/dotfiles
cd ~/projects/tickets_app
cd ~/projects/tickets_app/src
cd ~/projects/tickets
cd ~/projects/tickets/src

Now you can jump using the z command with the desired path hints:

z dot         # will jump to ~/dotfiles
z tic         # will jump to ~/projects/tickets
z tic app     # will jump to ~/projects/tickets_app
z tic app src # will jump to ~/projects/tickets_app/src

Though not Bash specific, the z utility is a fantastic tool that all Bash users will find useful.

Style

If you spend a lot of time in the command line then I recommend styling up the terminal to suit your needs.

Some suggestions:

Use a modern terminal and enable 256 colors.
Use a nice monospace font. I personally like the Menlo font on macOS and the Inconsolata font on Linux.
Configure the LS_COLORS environment variable to highlight filetypes using 256 colors.
Display useful information in your prompt. Examples being: hostname, username, filesystem path and git branch to name a few.
If you want to dabble into the world of Bash themes and other treats then have a look at Bash-it. Bash-it claims to be to Bash what oh-my-zsh is to Zsh. Personally I recommend configuring up the shell yourself, that will result in a leaner and faster shell.

Conclusion

With just a little effort the Bash shell will become a more enjoyable and productive environment.

The musings of bluz71