bash

• options
  • --: disable further option processing.
  • -i: interactive
  • -l: login-shell
• man [command] : show manual for command
• apropos [reg-exp]: search in the DESCRIPTION field of all manuals.

• shortcuts
  • ctrl-w delete last word
  • ctrl-a/e: move cursor to the beginning/ending.
  • ctrk-l: clear screen
  • alt-b/f: move cursor word-wise
  • alt-#: comment the current command and run it.
• !$ the parameters from the last command.
• pgrep -a [pattern]: list processes matching pattern. (a means list-all)
  • similar to ps aux | grep [pattern]
• pkill [pattern]: kill processes matching pattern.

• traceback bash error:

  set -euo pipefail
  trap "echo 'error: Script failed: see failed command above'" ERR
  

• locally move working directory:

  # do something in current dir
  (cd /some/other/dir && other-command)
  # continue in original dir
  

• login shells v.s. non-login shells

  • /etc/profile, ~/.profile, ~/.bash_profile: for login shells (the first process that executes under your user ID, e.g., by su or ssh)
  • ~/.bashrc: for interactive non-login shells (shells started in an existing session).

• sudo -u [user]: run command as user.

• repren: batch rename

  • [tbc]

• the fastest way to delete large amount of files:

  mkdir empty && rsync -r --delete empty/ some-dir && rmdir some-dir
  

• tac: reversed cat

• ncdu: n-curses version du.

• tar xf <file>: one command to uncompress all kind of tar/tar.xz/tar.gz