CLI - Tips & Tricks

PATH

Print all entries in $PATH line by line

# For bash, zsh
echo $PATH | sed 's/:/\n/g'

# For fish
echo $PATH | sed 's//\n/g'

# Output
/home/admin/.local/bin # The shell checks this directory first
/home/admin/bin
/usr/local/bin
/usr/local/sbin
/usr/bin
/usr/sbin

Command history

What is command history

(Almost) everything you type to the terminal is saved.

Where is the command history

The command history is stored at $HISTFILE, which by default:

• For bash, it’s ~/.bash_history,
• For zsh, it’s ~/..zsh_history,
• For fish, its’s ~/.local/share/fish/fish_history

How to use command history

• Access last command:

  • Press Arrow Up
  • Press Arrow Up more for last of last command
  • …

• Search for a command is the command history: Ctrl + R

  For a default bash, zsh prompt, it looks like this

  (reverse-i-search)`’:
  

• Use atuin¹ for a magical 🪄 shell history, which:

  • records additional context for your commands
  • synchronizes your history between machines/shells

Command completion

• Use Warp² terminal
• Use fish³ shell
• Use argc-completions⁴

How to know how to use a command?

• Use --help, -h, help flag/option/sub-command

  • Some commands support --help

    uname --help
    

    uname -h # Does't work
    

  • Some commands support -h

    dig -h
    

    dig --help # Doesn't work
    

  • Some commands support both --help, -h and even have a sub-command named help

    go help
    

    go -h
    

    go --help
    

  • Some commands don’t support --help or -h, and don’t have a help sub-command either, e.g. ssh, ssh-keygen

    $ ssh -h
    unknown option -- h
    

    $ ssh --help
    unknown option -- -
    

    $ ssh help
    ssh: Could not resolve hostname help: Name or service not known
    

• Access the command’s manual pages

  man uname
  

• Use tldr⁵, cheat⁶

  tldr uname
  

  cheat uname