Here is a list of linux cli commands/tools that I have used. Purpose is for my own future reference and to track what I know. The list is non exhaustive and not sorted in any way. explainshell.com is a very nice website to learn about the commands, can bookmark https://explainshell.com/explain?cmd=%s.

#Shell tools

  • man: get help for commands
  • which: get first path of command
  • where: get paths of command
  • alias: set command shortcut
  • whoami: get current user
  • watch: runs command every n seconds
    • watch -n5: runs command every 5 sec
  • tee: split stdin to file and stdout
  • xargs: reads stdin line by line and run command for every line
    • xargs -I{} <command> "{}": set each line as {} and run command with the line as first arg
  • set: sets shell options, usually used at the top of a bash script
    • set -euo pipefail: bash strict mode
    • set -euxo pipefail: bash strict mode, also prints each line
  • test: check condition and set exit code 0 for true, 1 for false, usually used in if statements
    • [: alias of test, for writing bash script like if [ condition ]
    • [[: better version of [

#Text operations

  • echo: prints text
  • cat: prints file content, also used for con”cat”enating files
  • less: reads file in a scrollable interface (ncurses), use j and k to scroll per line or u and d to scroll per page, q to quit
    • more: older version of less, cannot scroll up
  • head: reads first n lines
    • head -n5: reads first 5 lines
  • tail: reads last n lines
  • grep: find a word or with regex in files
  • sed: search and replace
  • tr: simpler alternative to sed
  • cut: split string and select substring
    • cut -d' ' -f1: split by space, select first word
  • awk: text manipulation tool, includes its own scripting language (heard of it, never used it)
  • sort: sort lines
  • uniq: deduplicate adjacent lines, usually used after sort
  • wc: word count
    • wc -l: line count
    • sort <file> | uniq | wc -l: count unique lines
  • jq: reads json and prints selected key, includes its own scripting language

#File operations

  • ls: prints directory listing
    • ls -lah: prints in detail
    • ls -lahtr: sorted by last modified (newest first)
  • cd: change directory
  • z: oh-my-zsh plugin to change to recent directory
  • rm: remove file/directory
    • rm -rf: removes recursively
  • cp: copies file
  • mv: moves file
  • mkdir: creates directory
  • pwd: prints working(current) directory, not to be confused with passwd
  • tar: compress or extract tar files
    • tar -xzvf: extracts .tar.gz files
  • gzip: compress or extract gzip files
    • gzip -d: extracts .gz file in the same dir, removing the .gz file
    • gzip -dk: extracts .gz file, keeping the .gz file
  • zless: less for .gz file without extracting it
  • zcat: cat for .gz file without extracting it
  • zgrep: grep for .gz file without extracting it
  • zip: compress to .zip
  • unzip: extracts .zip
  • touch: creates file, sets last modified time
  • chmod: change file permissions
    • chmod +x: make file executable
  • ln: creates symbolic link
  • find: find a file by filename

#System tools

  • uname: prints OS name
    • uname -a: prints all OS info
  • env: prints all env vars #!/usr/bin/env bash: runs bash specified in $PATH, usually used in first line of bash script
  • export: sets user env var
  • reboot: restarts machine
  • chroot: treat directory as fake root dir, containers are built upon this (heard of it, never used it)
  • lshw: lists all hardware info
  • lscpu: prints cpu info
  • df: show disk utilization

#Process tools

  • ps: list running processes
    • ps aux: list all
    • ps ef: alternative to ps aux
  • htop: like task manager in windows, view system resources
  • top: older colourless version of htop
  • dstat: prints system resource utilization every second
  • kill: kills process by sending SIGTERM
    • kill -9: kills using SIGKILL (cannot be caught by process)
    • kill -s: kills using specified signal

#Network tools

  • netstat: list open ports
    • netstat nltp: list all TCP listening ports and its process, may need sudo
  • ss: alternative to netstat
  • ifconfig: like ipconfig in windows, shows local IP address
  • ip: alternative to ifconfig
    • ip a: show ip address
  • ping: like ping in windows, sends ICMP packet to check if address is accessible and measure round trip time
  • tracert: measure hop by hop round trip time
  • dig: like nslookup in windows, runs dns lookup
  • ssh: provides a shell to access remote machine
  • scp: file transfer over ssh
  • rsync: more optimized alternative to scp
  • pssh: sends ssh commands in parallel to multiple machines
  • i2cssh: only for iterm2, opens multiple iterm2 panels to ssh into multiple machines (feels very hackery lol)
  • who: see who else is ssh-ing into the same machine
  • curl: send http request, also includes various other protocols
    • curl -fsSL: send request non verbose, follows http redirects
    • curl -X POST -d 'param1=value1&param2=value2': posts x-www-form-urlencoded
    • curl -X POST -H 'content-type: application/json' -d '{"a":"b"}': posts json
    • curl -F 'image=@file.jpg' -F 'param=value': posts multipart/form-data

#User permission

  • sudo: runs as root
    • sudo -s: change as root user, use my default shell, start in same directory
  • passwd: change password

#Other tools

  • bc: basic calculator
  • date: prints current datetime

#Shells

  • zsh: Z shell, popular cos of oh-my-zsh, default shell of MacOS, Arch
  • bash: Bourne again shell, popular cos default shell of Ubuntu
  • sh: symbolic link to default shell
  • fish: fish shell
  • chsh: change default shell

#Text editors

  • vim: very customizeable, not too beginner friendly text editor
  • vi: older alternative to vim
  • nvim: neovim, newer alternative to vim
  • nano: beginner friendly text editor

#Git

  • git: version control system, best to alias all the commands using oh-my-zsh git plugin
    • git status: show status
    • git log: show commit history
      • git log --all --decorate --oneline --graph: pretty log
    • git add: stages file
    • git commit: commits staged changes
      • git commit -m:
      • git commit --amend --no-edit: rewrite previous commit with staged changes
    • git push: pushes commits
      • git push -f: force overwrite remote commits
      • git push --force-with-lease: force if no newer commits on remote
    • git pull: pulls commits
    • git reset: unstage changes
      • git reset HEAD~: undo previous commit
      • git reset --hard HEAD~: undo previous commit and undo changes in working directory
    • git checkout: change branch
      • git checkout -b: create new branch and change branch
    • git merge: merge branches
    • git remote: show remote name
      • git remote -v: list remote repos
    • git rebase: moves branch’s base commit up to latest by rewriting commits, good for keeping clean history, bad if you’re working in a team
      • git rebase -i: interactive rebase
      • git rebase --abort: cancel ongoing rebase
    • git reflog: list history of commits accessed in local repo, useful if you lost reference due to rebase or if you mess up rebasing

#Docker

  • docker: for docker containers
    • docker pull: downloads image
    • docker run: run container
      • docker run -it <container> /bin/bash: enter the container (like ssh into container)
    • docker images: list images
    • docker ls: list containers
    • docker login: saves credential to remote docker registry (for pulling/pushing images)

#Package managers

  • apt: for ubuntu
  • brew: for mac
  • npm: for nodejs
  • pip: for python
    • python -m venv .venv: create virtual env . .venv/bin/activate: enter virtual env
    • virtualenv -p <path to python2> .venv: create virtual env for python2
  • cargo: for rust
  • go get: for golang
  • gem: for ruby
  • fpm: effing package management, creates various packages

#Version managers

  • pyenv: for python
  • rbenv: for ruby
  • rvm: alternative to rbenv
  • nvm: for nodejs

#Fancy tools

  • ranger: file explorer in terminal
  • ncmpcpp: mpd client for playing music in terminal