Beyond Bash

Eduardo Bellido Bellido

http://edubxb.net

@edu2b

by

About bash

• Free software
• Part of the GNU Project
• Default shell in GNU/Linux and Mac
• Available in other OS (Windows included)
• Shell Shock

Why bash?

• Plenty of features
• Always available, no need to learn new things
• GNU readline powered
• Extensible like other popular shells (zsh, fish)

GNU Readline library

• Provides the advanced editing options, history, and other capabilities to Bash
• Used by many projects, not only Bash
• Very configurable

Time to improve!

Configuration

Config files

When bash starts as login shell:

  ~/.bash_profile

When bash starts interactively:

  ~/.bashrc

GNU Readline config file:

  ~/.inputrc

Simplify things

Put all your configuration in .bashrc

Then, in .bash_profile, put:

if [ -f ~/.bashrc ]; then
    source ~/.bashrc
fi

More info: https://www.gnu.org/software/bash/manual/bashref.html#Bash-Startup-Files

Useful options

autocd → enter directories without typing cd

cdspell → correct minor spelling errors in directory names

extglob → enable extended pattern matching features

globstar → enable the pattern '**'

histappend → history list is appended rather than overwrited

Know your history

Don't repeat yourself

View your history

$ history
1 cd /tmp
2 wget https://www.kernel.org/pub/linux/kern
  el/v4.x/linux-4.0.4.tar.xz
3 tar xvJf linux-4.0.4.tar.xz
4 cd linux-4.0.4
5 make oldconfig
6 make -j 4
7 make modules_install
8 make install

# append history lines from current session to the history file
$ history -a

# read the history file and append the contents to the history list
$ history -r

Repeat your history

!n → Refer to command line n

!-n → Refer to the current command minus n

!! → Refer to the previous command (tip: sudo !!)

!string → Refer to the most recent command preceding the current position in the history list starting with string

!?string[?] → Refer to the most recent command preceding the current position in the history list containing string

^string1^string2^ → Repeat the previous command, replacing string1 with  string2

More info: https://www.gnu.org/software/bash/manual/bashref.html#Event-Designators

Navigating the history

C-p → Move 'back' through the history list, fetching the previous command

C-n → Move 'forward' through the history list, fetching the next command

M-< → Move to the first line in the history

M-> → Move to the end of the input history, i.e., the line currently being entered

C-r → Search backward starting at the current line and moving 'up' through the history as necessary

C-s → Search forward starting at the current line and moving 'down' through the the history as necessary (try "stty -ixon" if doesn't work)

C-g → Escape from history searching mode

More info: https://www.gnu.org/software/bash/manual/bashref.html#Commands-For-History

A better history

More info: https://www.gnu.org/software/bash/manual/bashref.html#Bourne-Shell-Variables

HISTCONTROL='ignorespace:ignoredups:erasedups'
HISTSIZE=1000
HISTFILESIZE=3000
HISTTIMEFORMAT='[%F %T]  '

Some variables to control the history behavior:

Meet the "magic-space"

Expands the history commands

Enable it:

# Add those lines to your .inputrc file
$if Bash
  Space: magic-space
$endif

Movement & Edition

be faster!

Basic movements

C-a → Move to the start of the current line
C-e → Move to the end of the line
C-f → Move forward a character
C-b → Move back a character
M-f → Move forward to the end of the next word
M-b → Move back to the start of the current or previous word

Basic edition

M-Del → Delete the Word before the cursor
M-d → Delete the Word after the cursor
C-d → Delete character under the cursor
C-h → Delete character before the cursor (Backspace)

C-w → Cut the Word before the cursor to the clipboard
C-k → Cut the Line after the cursor to the clipboard
C-u → Cut/delete the Line before the cursor to the clipboard

C-y → Paste the last thing to be cut (yank)
C-_ → Undo

Patterns & Expansions

Extended patterns

?(pattern-list)

    Matches zero or one occurrence of the given patterns

*(pattern-list)

    Matches zero or more occurrences of the given patterns

+(pattern-list)

    Matches one or more occurrences of the given patterns

@(pattern-list)

    Matches one of the given patterns

!(pattern-list)

    Matches anything except one of the given patterns

Useful expansions I

${parameter:=word}

    Assign Default Values

${parameter:offset}

${parameter:offset:length}

    Substring  Expansion

More info: http://www.gnu.org/software/bash/manual/html_node/Shell-Parameter-Expansion.html

Useful expansions II

${parameter#word}

${parameter##word}

    Remove matching prefix pattern

${parameter%word}

${parameter%%word}

    Remove matching suffix pattern

${parameter/pattern/string}

    Pattern substitution

More info: http://www.gnu.org/software/bash/manual/html_node/Shell-Parameter-Expansion.html

Useful expansions III

${parameter^pattern}

${parameter^^pattern}

${parameter,pattern}

${parameter,,pattern}

    Case  modification

More info: http://www.gnu.org/software/bash/manual/html_node/Shell-Parameter-Expansion.html

Extending bash

Cool projects to try

Questions?

Thanks!

$ sudo applause