Yet Another Guide About Bash tricks

“ Shell leads the willing and drags along the reluctant “ -maybe Seneca

Nowadays, working with a shell is an inherent part of the everyday life of a software engineer, therefore, I would dare to say that any “trick” that can improve the general speed or knowledge regarding this matter is rather important.

Without further ado, I will share a compilation of different commands which has helped me greatly.

10 Bash Commands to Improve Speed

Go Back to the Previous Directory

Going back to the previous directory (based on $OLDPWD internal variable) - especially useful when navigating through long paths:

cd -

2. Execute Your Last Command

Execute last command - useful for rerunning the previous command:

!!

3. Check the Return Code of Your Last Command

Check the return code of the last command - useful when checking various return codes (in Unix and Linux, every command returns a numeric code between 0-255):

echo $?

4. Get the Process ID

Get the Process ID of this shell itself - SHELL is not always defined by the bash shell:

# echo $SHELL
ps -p $(echo $$)
PID TTY          TIME CMD
26719 pts/0    00:00:01 bash

5. Execute the Emulating Tree Command

Emulating tree command - on minimal distros, tree command may not exists, therefore the following alias provides the much needed recursive directory listing:

alias tree='function tree(){ find ${1:-.} | sed -e "s/[^-][^\/]*\//  |/g" -e "s/|\([^ ]\)/|-\1/"; unset -f tree;}; tree'

6. Ad-hoc YAML Linter

Ad-hoc YAML linter as alias - not a proper linter but useful for quick check of various YAML files:

alias ymllint='python -c "import sys,yaml as y;y.safe_load(open(sys.argv[1]))"'

7. Ad-hoc JSON Linter

Ad-hoc JSON linter as alias - based on jq JSON processor:

alias jsonl='jq "." >/dev/null <'

8. Set the Sell

Set the sell to work in either vi or emacs mode - no debate is needed:

# echo $SHELLOPTS to check
set -o vi
set - o emacs

9. Globbing

globbing “searching for files using wildcard expansion”-list files that start with the lettera:

# * matches any sequence of characters
ls a*

10. Create a Nested Structure

Creating a nested structure of directories:

mkdir -p provisioning/{datasources,notifiers,dashboards/backup}

# will create
.
└── provisioning
    ├── dashboards
    │   └── backup
    ├── datasources
    └── notifiers

11. Reverse search

Want to re-run a lengthier and complicated command and reverse-search (CTRL+R) is not enough, just use history to list the previously used commands and then !<line_no>

to re-run command or !<line_no>:pto print the command without running it:

" Shell alone is eternal, perpetual, immortal" - maybe Schopenhauer