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Bash - Bourne again shell

Bash is the default shell of most Linux distros.

  • Ctrl + a → Go to the beginning of the line
  • Ctrl + e → Go to the end of the line
  • Alt + f → Move cursor to the next word
  • Alt + b → Move cursor to the previous word
  • Ctrl + x, x → Move cursor between the current position and the begining of the line

Editing​

  • Ctrl + k → Cut line after cursor and copy it to the clipboard
  • Ctrl + u → Cut line before cursor and copy it to the clipboard
  • Ctrl + y → Paste what you have on the clipbaord
  • Ctrl + _ → Undo your last key press

Processing​

  • Ctrl + c → Kill the currently running command
  • Ctrl + d → Exit the shell
  • Ctrl + l → Clear the screen (Same as the clear command)

History​

  • Alt + p → Search backward through the history starting at the current line
  • Alt + n → Search forward through the history starting at the current line
  • Ctrl + r → Open the history search

Tips​

Install Bash-completion​

Bash-completion helps you type commands faster and easiler.

# Ubuntu
sudo apt install bash-completion

# Rocky
sudo dnf install bash-completion

Press [TAB] when you type commands, for example:

sudo git [TAB]
sudo systemctl [TAB]

History search with arrow keys​

You can enable arrow keys -- [Up] for backward and [Down] for forward -- for history search by these commands (You can put them in your .bashrc.)

bind '"\e[A": history-search-backward'
bind '"\e[B": history-search-forward'

Write a file in a script​

Create a new file / Overwrite an existing file

## tee
tee /tmp/test.txt <<EOF
This is the 1st line
This is the 2nd line
EOF
# cat
cat <<EOF> /tmp/test.txt
This is the 1st line
This is the 2nd line
EOF

Append new lines

# tee
tee -a /tmp/test.txt <<EOF
This is the 3rd line
This is the 4th line
EOF
# cat
cat <<EOF>> /tmp/test.txt
This is the 3rd line
This is the 4th line
EOF

I prefer using tee because tee also prints these lines to stdout.

Array in Bash script​

test_array.sh
myArray=("cat" "dog" "mouse" "frog")

echo ${myArray[@]}
echo ${!myArray[@]}

for str in ${myArray[@]}; do
  echo $str
done

for i in ${!myArray[@]}; do
  echo "element $i is ${myArray[$i]}"
done

Make your bash script safer​

#!/bin/bash

set -euxo pipefail

  • -e → Exit immediately if a command exits with a non-zero status.
  • -u → Treat unset variables as an error when substituting.
  • -x → Print commands and their arguments as they are executed.
  • -o pipfail → The return value of a pipeline is the status of the last command to exit with a non-zero status, or zero if no command exited with a non-zero status.

Get the directory path where a script is located​

#!/bin/bash

SCRIPT_DIR="$( cd "$( dirname "${BASH_SOURCE[0]}" )" &> /dev/null && pwd )"
echo "Script directory: $SCRIPT_DIR"