Bash Tips and Tricks

Bash, Linux, Terminal

There are loads of tutorials on bash. This does not aim to be a reference guide instead aims to show some lesser known commands that can be super powerful if used right.

Brace expansion

With the {} symbol you can specify a brace expansion.

It can be used with number ranges and strings.
Its most useful with numbers in my opinion.
You can specify a range with ...

Examples:

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# Echo the integers from 1 to 100
echo {1..100} # 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 # 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 # 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 # 91 92 93 94 95 96 97 98 99 100

# Create a 100 files with numbers in their names
touch file_{1..100}

# Increment from 1 to 10 by 2
echo {1..10..2} # 1 3 5 7 9

Brace expansion ranges also work with letters.

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echo {A..z} # A B C D E F G H I J K L M N O P Q R S T U V W X Y Z [  ] ^ _ ` a b c d e f g h i j k l m n o p q r s t u v w x y z

You can also use brace expansion with strings.
Without the optional preamble and postscript strings, the result is just a space-separated list of the given strings.
You can add a preamble and postscript tag to generate all possible combinations.

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 echo 1{a,b,c}2 #1a2 1b2 1c2

You can find more about brace expansions here.

-

You can use the - symbol to reference the last working directory.
You can use this to toggle between two directories.

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cd ~
cd dir1
cd - # ~
cd - # dir1

The - basically replaces the $OLDPWD environment variable.

logger

You can send messages straight to the syslog.
If you want to debug a script which gets run from cron you can simply use logger to print a message.

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logger 'myscript.sh' 'im a new message' -i

This creates an entry in /var/log/syslog on Ubuntu.
You can check it with the following command.

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tail /var/log/syslog

You can add priority with the -p flag.
If you set the priority to 0 a message gets broadcasted.

You can find more info about logger here: man 1 logger

file

You can get the type of a file with the file command.

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file initrd.img-4.6.0-040600-generic # initrd.img-4.6.0-040600-generic: gzip compressed data

Clipboard integration

On ubuntu you have xclip for copy pasting.

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sudo apt install xclip
ls | xclip -selection clipboard # Copy the output of the command to the clipboard
xclip -selection clipboard -o > file # Write the stuff in your clipboard to a file

You can create aliases for easier use.

In ~/.bashrc

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alias xcopy='xclip -selection clipboard'  # Copy 
alias xpaste='xclip -selection clipboard -o'  # Paste

Keybindings

There are loads of key combinations you can use.

Key Combination Effect
ctrl + a move the cursor to the start of the line
ctrl + e move the cursor to the end of the line
ctrl + -> jump to the start of the word on the right
ctrl + <- jump to the start of the word on the left
delete delete the next character to the right
shift + delete delete the next character to the left (same as backspace)
alt + d delete from the cursor to the end of the word to the right
alt + backspace delete the next word to the left
ctrl + k delete everything to the right from the current cursor position
ctrl + u delete everything to the left from the the current cursor position
alt + . add the argument of the last command to the end of the current command
ctrl + y paste the last command into the current buffer