Linux/Shell

Table of Contents

• Table of Contents
• Interesting threads
• Bash
• Zsh + Oh-my-zsh + Powerlevel10k
• All Terminals
• Nano
• Top
• Man pages

Interesting threads

• https://stackoverflow.com/a/42082956/10699128
  • “Difference between single and double quotes in Bash”
  • Comprehensive explanation of variable evaluation
  • "", '', $, \
• https://unix.stackexchange.com/a/444949/379903
  • “How can we run a command stored in a variable?”
  • Comprehensive explanation of functions
  • definition, evaluation, arguments

Bash

Make .sh script fail on error (and not continue like nothing happened)!

• set -euo pipefail
  • -e
    • exit immediately on error
  • -u
    • fail on unset variables
  • -o pipefail
    • fail on failed pipes
  • -x
    • before executing it command print it with arguments to stderr (like debug mode)
• More info:
  https://www.gnu.org/software/bash/manual/html_node/The-Set-Builtin.html

Complex alias

In general

 aliasname() {
     command --firstParam --secondParam
 }

Example

getaks() {
    az aks list -g $1 -o $2
}

Pass all arguments to alias

• Use $@

maven() {
  mvn -T1C "$@"
}

effect: maven install -DskipTests
becomes: mvn -T1C install -DskipTests

Function arguments

• List:
  • $@ - stores all the arguments in a list of string
  • $* - stores all the arguments as a single string
  • $# - stores the number of arguments
  • "$@" is actually not a list of strings, but a list of arguments.
• $@ expands to the arguments passed from the caller to a function or a script.
  • Inside a function, it expands to the arguments passed to such function.
  • If used in a script (outside a function), it expands to the arguments passed to such script.

Check if file exists

if ! [ -f ./resources/$ARCHIVE ]; then
  curl --output ./resources localhost:8080/archive.zip
fi

Zsh + Oh-my-zsh + Powerlevel10k

1. You can shorthand autocomplete paths inside commands, like:
   • cd /h/k/.s/
     -> cd /home/komidawi/.ssh
2. History search by starting fragment
   • Example:

       nano /home/komidawi/.ssh/known_hosts
       nano /etc/hosts
     
       nano /h<UP>
     

     will auto-complete into

       nano /home/komidawi/.ssh/known_hosts
     

3. Show n last history entries (0 shows all)
   • history n
4. Expand envs
   • $USER<TAB>
     -> komidawi
5. Print parameters help cat -<TAB>

    --help                  -- display help and exit
    --number            -n  -- number all output lines
    --number-nonblank   -b  -- number nonempty output lines, overrides -n
    --show-all          -A  -- equivalent to -vET
    --show-ends         -E  -- display $ at end of each line
   

6. Use take to mkdir and cd into it
   • take folder/subfolder/finish
   • it also works with zip archives, git repos and url downloads
7. Command history
   • Ctrl + R
   • Press again for next occurrence
8. Quick cd
   • You can move into folders by name of the folder without cd
9. List last visited dirs
   1. d (shortcut for dirs -v)
10. Command parking
    • Press Ctrl + Q to hide current command
    • After invoking another command, the first one comes back
11. Open command in editor
    • Ctrl + X, Ctrl + E
    • Opens in default editor ($EDITOR)
    • Useful for long commands
12. cd shortcuts
    • cd ....
      -> moves 4 levels up
    • cd -
      -> jumps to previous path
13. Extensive search
    • ls *.txt
      -> text files
    • ls **/*.txt
      -> text files (also within subdirectories)
    • ls **/(START)*.* -> files starting with word START
    • ls **/*(END).* -> files ending with word END
    • ls **/*(WORD)*.* -> files with WORD
    • ls **/*(.) -> search only files
    • ls **/*(/) -> search only folders
14. List recently open directories
    1. d
15. Copy to clipboard (WSL2)
    1. command | clip.exe

All Terminals

1. Pretty format JSON
   • Use JQ, e.g.:
     • cat file.json | jq
   • Just colorize:
     • jc -c

Nano

1. Search a phrase
   • Ctrl + W
2. Search next occurrence
   • Ctrl + W
   • F6
3. Previous occurrence
   • Alt + Q
4. Show help
   • F1
5. Show navigation help
   • h

Top

1. Show process tree
   • Shift + V
2. Sort by CPU usage
   • Shift + P
3. Sort by Memory usage
   • Shift + M
4. Kill process
   • k

Man pages

1. Search
   • /<phrase>, Enter
2. Next occurrence
   • n