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Wednesday, 26 October 2016

Awesome Shell

A curated list of awesome command-line frameworks, toolkits, guides and gizmos.


A curated list of awesome command-line frameworks, toolkits, guides and gizmos. Inspired by awesome-php. This awesome collection is also available on

Command-Line Productivity

Search, bookmarks, multiplexing, and other tools that make your terminal experience more productive.
  • ag - Super fast string search through a directory hierarchy
  • aliases - Contextual, dynamic, organized aliases for bash
  • aliasme - alias helper to change directory quickly
  • autoenv - Directory-based environments
  • autojump - A cd command that learns - easily navigate directories from the command line
  • bashhub - ☁️ Bash history in the cloud. Indexed and searchable.
  • bashmarks - Directory bookmarks for the shell
  • bd - Quickly go back to a parent directory
  • boilr - A blazingly fast CLI tool for creating projects from boilerplate templates.
  • boom - Store links and snippets in the commandline
  • borg - A terminal based search engine for bash commands
  • byobu - Text-based window manager and terminal multiplexer
  • commacd - A faster way to move around in Bash
  • desk - A lightweight workspace manager for the shell
  • direnv - An environment switcher for the shell, compare with autoenv
  • enhancd - 🚀 A next-generation cd command with an interactive filter
  • fasd - Command-line productivity booster, offers quick access to files and directories
  • foxy - Plain text bookmarks for firefox and surf browsers.
  • fzf - A command-line fuzzy finder
  • hhighlighter - Colorize words in a command output
  • hr - <hr /> for your terminal
  • hstr - Bash History Suggest Box
  • k - k is a Zsh script to make directory listings more readable, adding Git status, fileweight colors and rotting dates
  • k alias - get kool aliases (and more) working with a simple one-liner
  • marker - Bookmark your shell commands
  • parallel - Build and execute shell command lines from standard input in parallel
  • pathpicker - Accepts inputs like grep, searches, git etc; allows selecting files from the result of the input, which you can then open or provide as argument to a command.
  • percol - Adds flavor of interactive filtering to the traditional pipe concept of UNIX shell
  • qfc - File-completion widget for Bash and Zsh
  • SHML - Style framework for the terminal (Shell Markup Language)
  • slugify - Command that converts filenames and directories to a web friendly format
  • sman - 🐛 A command-line snippet manager
  • spark - ▁▂▃▅▂▇ in your shell
  • Shark - ▁▂▃▅ Sparkline Generator
  • sheet - Text snippets for the command line
  • spot - Tiny file search utility
  • snips - Commandline tool to manage snippets of code.
  • sshfs - A tool for mounting remote file systems over SSH
  • sshrc - Bring your .bashrc, .vimrc, etc. with you when you SSH
  • sudocabulary - Learn English Vocabulary from your terminal
  • thefuck - Fix common shell mistakes by using an easy to remember command
  • tmux - Amazing terminal multiplexer
  • up - Ascend directories by name or count, for bash and zsh.
  • v - z for vim.
  • wemux - Multi-User Tmux Made Easy
  • z - z is the new j, yo


Custom prompts, color themes, etc.

For Developers

Command-line development, version control, and deployment.
  • bocker - Docker implemented in 100 lines of bash
  • cloc - Count Lines of Code
  • dokku - Docker powered mini-Heroku. The smallest PaaS implementation you've ever seen.
  • getopts - CLI parser for fish
  • git-extra-commands - Many Git extra utilities. Churn, cut-branch, improved-merge and many more.
  • git-extras - Git utilities -- repo summary, repl, changelog population, author commit percentages and more
  • git-open - Type git open to open the GitHub page or website for a repository in your browser
  • git-semver - Git plugin for easing semantic versioning and changelog validation
  • git-sh - A customized Bash environment suitable for Git work
  • git-up - Automatically rebase incoming changes instead of merging. Be polite!
  • hub - hub helps you win at git.
  • mr - Multiple Repository management tool
  • overcommit - A fully configurable and extendable Git hook manager
  • pre-commit - A framework for managing and maintaining multi-language pre-commit hooks
  • repren - Command-line search-and-replace and file-renaming swiss army knife
  • slap - Sublime-like terminal-based text editor that runs on Node.js
  • shipit - Minimalistic SSH deployment

System Utilities

OS-related tools, including system administration, system debugging, and file and process management.
  • atop - ASCII full-screen performance monitor that is capable of reporting the activity of all processes
  • cv - Linux tool to show progress for cp, rm, dd, ...
  • glances - Glances an Eye on your system
  • goaccess - GoAccess is a real-time web log analyzer and interactive viewer that runs in a terminal in *nix systems.
  • histstat - History for netstat
  • htop - A ncurses based interactive process viewer which aims to be a better top
  • lnav - An advanced log file viewer for the small-scale
  • lsp - An improved ls, with file descriptions in plain language and intelligent file grouping
  • mtr - The functionality of the 'traceroute' and 'ping' programs in a single network diagnostic tool.
  • ncdu - NCurses Disk Usage
  • powertop - Battery/Power usage and device stats monitoring command-line tool, with tune-up options.
  • procdog - Lightweight command-line control of long-lived processes like servers
  • quick-secure - Quickly secure and harden UNIX/Linux systems

Downloading and Serving

Self-hosted, lightweight servers and networking tools written in shell scripts.
  • aria2 - aria2 is a lightweight multi-protocol & multi-source, cross platform download utility operated in command-line. It supports HTTP/HTTPS, FTP, BitTorrent and Metalink
  • balls - Bash on Balls
  • bashttpd - A web server written in Bash
  • bitpocket - "DIY Dropbox" or "2-way directory (r)sync with proper deletion"
  • Dropbox-Uploader - Dropbox Uploader is a Bash script which can be used to upload, download, list or delete files from Dropbox
  • httpie - HTTPie is a command line HTTP client, a user-friendly cURL replacement
  • ngincat - Tiny Bash HTTP server using netcat
  • resty - Little command line REST client that you can use in pipelines
  • youtube-dl - Small command-line program to download videos from and other video sites

Multimedia and File Formats

Tools for handling video and audio files.
  • adb-export - Export Android content providers to CSV format
  • Android-Kitchen - A text-based kitchen for Android ROM customization. Uses shell scripts and works with Cygwin/OS X/Linux
  • Beets - Music library manager and MusicBrainz tagger
  • cmus - Cross-platform cli audio player.
  • gifgen - Simple high quality GIF encoding
  • image-scraper - A cool command line image scraper with a lot of features.
  • jq - Sed for json data. You can use it to slice and filter and map and transform structured data
  • mplayer - Lets you play most audio and video formats (using ASCII characters) in the shell as well as in a GUI.
  • nehm - Console tool, which downloads, sets IDv3 tags and adds to your iTunes (if you use it) your SoundCloud likes in convenient way
  • PiCAST - PiCAST turns your $35 Raspberry Pi in to a Chromecast like Device
  • sejda - Command line manipulation of PDF documents (split, merge, rotate, convert to jpg, extract text, etc)
  • xmlstarlet - Old but powerful tool for command-line XML formatting, filtering, and manipulation.


Command line-based applications or command line access to existing services.
  • ansiweather - Weather in your terminal, with ANSI colors and Unicode symbols
  • bashblog - A Bash script that handles blog posting
  • choosealicense-cli - Bring to your terminal
  • facy - Command line power tool for facebook
  • fanyi - Translate English to Chinese in terminal
  • geeknote - Command line evernote client
  • haxor-news - Browse Hacker News like a haxor
  • hn-cli - Browse Hacker News from the comfort of your Terminal
  • iponmap - Draw point on world map using ip address
  • isitup - Check whether a website is up or down
  • jrnl - A simple command line journal application that stores your journal in a plain text file
  • ledger - Command line accounting
  • licen - Generate your license. Yet another lice, but implement with Jinja2 and docopt
  • moviemon - Everything about your movies within the command line.
  • pushblast - Get PushBullet notifications when a shell program exits
  • pushbullet-bash - Bash interface to the PushBullet API
  • Reddit Terminal Viewer - Browse Reddit from your terminal
  • SAWS - A Supercharged AWS CLI
  • — Quickly upload and share files from your shell
  • vl - URL link checker on text documents
  • wego - Weather app for the terminal
  • whereami - Get your geolocation information from the CLI


All work and no play is a cruddy way to spend your day.

Shell Package Management

Tools for managing multiple shell configurations. For zsh-specific tools, see the Zsh section.
  • bash-it - A community Bash framework
  • basher - A package manager for shell scripts
  • bpkg - JavaScript has npm, Ruby has Gems, Python has pip and now Shell has bpkg
  • dotfiler – Shell agnostic git based dotfiles package manager, written in Python.
  • fresh - Keep your dotfiles fresh
  • homeshick - Git dotfile synchronizer written in Bash
  • vcsh - Config manager based on Git
  • shundle - Plugin manager for shell scripts

Shell Script Development

Tools for writing, improving, or organizing Bash or other shell scripts
  • ansi - ANSI escape codes in pure bash - change text color, position the cursor, much more
  • - Bash unit testing framework
  • bashful - A collection of libraries to simplify writing Bash scripts
  • bashmanager - mini bash framework for creating command line tools
  • bats - Bash Automated Testing System
  • Fishtape - TAP producer and test harness for fish
  • composure - Compose, document, version and organize your shell functions
  • dispatch - A command line argument parser in 50 lines of portable shell script.
  • - An alternative for builtin test command, it will make your "if" statements pretty
  • mo - Mustache templates in pure bash
  • optparse - A BASH wrapper for getopts, for simple command line arguments.
  • rerun - A modular shell automation framework to organize your keeper scripts
  • semver_bash - Semantic Versioning in Bash
  • sh-semver - Semver tool for bash - finds versions matching to specified rules
  • shellcheck - Static analysis tool for shell scripts
  • shellfire - A repository of namespaced, composable shell (bash, sh and dash) function libraries
  • shpec - A shell testing framework
  • sub - A delicious way to organize programs
  • ts - A shell test script
  • shunit2 - A unit test framework for Bash scripts with a flavour of JUnit/PyUnit.
  • rebash - Scripting library/framework. Features: imports, exceptions, doc-tests ...



The Art of Command Line

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Fluency on the command line is a skill often neglected or considered arcane, but it improves your flexibility and productivity as an engineer in both obvious and subtle ways. This is a selection of notes and tips on using the command-line that we've found useful when working on Linux. Some tips are elementary, and some are fairly specific, sophisticated, or obscure. This page is not long, but if you can use and recall all the items here, you know a lot.
This work is the result of many authors and translators. Some of this originally appeared on Quora, but it has since moved to GitHub, where people more talented than the original author have made numerous improvements. Please submit a question if you have a question related to the command line. Please contribute if you see an error or something that could be better!


  • This guide is both for beginners and the experienced. The goals are breadth (everything important), specificity (give concrete examples of the most common case), and brevity (avoid things that aren't essential or digressions you can easily look up elsewhere). Every tip is essential in some situation or significantly saves time over alternatives.
  • This is written for Linux, with the exception of the "OS X only" and "Windows only" sections. Many of the other items apply or can be installed on other Unices or OS X (or even Cygwin).
  • The focus is on interactive Bash, though many tips apply to other shells and to general Bash scripting.
  • It includes both "standard" Unix commands as well as ones that require special package installs -- so long as they are important enough to merit inclusion.
  • To keep this to one page, content is implicitly included by reference. You're smart enough to look up more detail elsewhere once you know the idea or command to Google. Use apt-getyumdnfpacmanpip or brew (as appropriate) to install new programs.
  • Use Explainshell to get a helpful breakdown of what commands, options, pipes etc. do.


  • Learn basic Bash. Actually, type man bash and at least skim the whole thing; it's pretty easy to follow and not that long. Alternate shells can be nice, but Bash is powerful and always available (learning only zsh, fish, etc., while tempting on your own laptop, restricts you in many situations, such as using existing servers).
  • Learn at least one text-based editor well. Ideally Vim (vi), as there's really no competition for random editing in a terminal (even if you use Emacs, a big IDE, or a modern hipster editor most of the time).
  • Know how to read documentation with man (for the inquisitive, man man lists the section numbers, e.g. 1 is "regular" commands, 5 is files/conventions, and 8 are for administration). Find man pages with apropos. Know that some commands are not executables, but Bash builtins, and that you can get help on them with help and help -d. You can find out whether a command is an executable, shell builtin or an alias by using type command.
  • Learn about redirection of output and input using > and < and pipes using |. Know > overwrites the output file and >> appends. Learn about stdout and stderr.
  • Learn about file glob expansion with * (and perhaps ? and [...]) and quoting and the difference between double " and single ' quotes. (See more on variable expansion below.)
  • Be familiar with Bash job management: &ctrl-zctrl-cjobsfgbgkill, etc.
  • Know ssh, and the basics of passwordless authentication, via ssh-agentssh-add, etc.
  • Basic file management: ls and ls -l (in particular, learn what every column in ls -l means), lessheadtail and tail -f (or even better, less +F), ln and ln -s (learn the differences and advantages of hard versus soft links), chownchmoddu (for a quick summary of disk usage: du -hs *). For filesystem management, dfmountfdiskmkfslsblk. Learn what an inode is (ls -i or df -i).
  • Basic network management: ip or ifconfigdig.
  • Learn and use a version control management system, such as git.
  • Know regular expressions well, and the various flags to grep/egrep. The -i-o-v-A-B, and -C options are worth knowing.
  • Learn to use apt-getyumdnf or pacman (depending on distro) to find and install packages. And make sure you have pip to install Python-based command-line tools (a few below are easiest to install via pip).

Everyday use

  • In Bash, use Tab to complete arguments or list all available commands and ctrl-r to search through command history (after pressing, type to search, press ctrl-r repeatedly to cycle through more matches, press Enter to execute the found command, or hit the right arrow to put the result in the current line to allow editing).
  • In Bash, use ctrl-w to delete the last word, and ctrl-u to delete all the way back to the start of the line. Use alt-b and alt-f to move by word, ctrl-a to move cursor to beginning of line,  ctrl-e to move cursor to end of line, ctrl-k to kill to the end of the line, ctrl-l to clear the screen. See man readline for all the default keybindings in Bash. There are a lot. For example alt-. cycles through previous arguments, and alt-* expands a glob.
  • Alternatively, if you love vi-style key-bindings, use set -o vi (and set -o emacs to put it back).
  • For editing long commands, after setting your editor (for example export EDITOR=vim), ctrl-x ctrl-e will open the current command in an editor for multi-line editing. Or in vi style, escape-v.
  • To see recent commands, use history. Follow with !n (where n is the command number) to execute again. There are also many abbreviations you can use, the most useful probably being !$ for last argument and !! for last command (see "HISTORY EXPANSION" in the man page). However, these are often easily replaced with ctrl-r and alt-..
  • Go to your home directory with cd. Access files relative to your home directory with the ~ prefix (e.g. ~/.bashrc). In sh scripts refer to the home directory as $HOME.
  • To go back to the previous working directory: cd -.
  • If you are halfway through typing a command but change your mind, hit alt-# to add a # at the beginning and enter it as a comment (or use ctrl-a#enter). You can then return to it later via command history.
  • Use xargs (or parallel). It's very powerful. Note you can control how many items execute per line (-L) as well as parallelism (-P). If you're not sure if it'll do the right thing, use xargs echo first. Also, -I{} is handy. Examples:
      find . -name '*.py' | xargs grep some_function
      cat hosts | xargs -I{} ssh root@{} hostname
  • pstree -p is a helpful display of the process tree.
  • Use pgrep and pkill to find or signal processes by name (-f is helpful).
  • Know the various signals you can send processes. For example, to suspend a process, use kill -STOP [pid]. For the full list, see man 7 signal
  • Use nohup or disown if you want a background process to keep running forever.
  • Check what processes are listening via netstat -lntp or ss -plat (for TCP; add -u for UDP).
  • See also lsof for open sockets and files.
  • See uptime or w to know the how long the system has been running.
  • Use alias to create shortcuts for commonly used commands. For example, alias ll='ls -latr' creates a new alias ll.
  • Save aliases, shell settings, and functions you commonly use in ~/.bashrc, and arrange for login shells to source it. This will make your setup available in all your shell sessions.
  • Put the settings of environment variables as well as commands that should be executed when you login in ~/.bash_profile. Separate configuration will be needed for shells you launch from graphical environment logins and cron jobs.
  • Synchronize your configuration files (e.g. .bashrc and .bash_profile) among various computers with Git.
  • Understand that care is needed when variables and filenames include whitespace. Surround your Bash variables with quotes, e.g. "$FOO". Prefer the -0 or -print0 options to enable null characters to delimit filenames, e.g. locate -0 pattern | xargs -0 ls -al or find / -print0 -type d | xargs -0 ls -al. To iterate on filenames containing whitespace in a for loop, set your IFS to be a newline only using IFS=$'\n'.
  • In Bash scripts, use set -x (or the variant set -v, which logs raw input, including unexpanded variables and comments) for debugging output. Use strict modes unless you have a good reason not to: Use set -e to abort on errors (nonzero exit code). Use set -u to detect unset variable usages. Consider set -o pipefail too, to on errors within pipes, too (though read up on it more if you do, as this topic is a bit subtle). For more involved scripts, also use trap on EXIT or ERR. A useful habit is to start a script like this, which will make it detect and abort on common errors and print a message:
      set -euo pipefail
      trap "echo 'error: Script failed: see failed command above'" ERR
  • In Bash scripts, subshells (written with parentheses) are convenient ways to group commands. A common example is to temporarily move to a different working directory, e.g.
      # do something in current dir
      (cd /some/other/dir && other-command)
      # continue in original dir
  • In Bash, note there are lots of kinds of variable expansion. Checking a variable exists: ${name:?error message}. For example, if a Bash script requires a single argument, just write input_file=${1:?usage: $0 input_file}. Using a default value if a variable is empty: ${name:-default}. If you want to have an additional (optional) parameter added to the previous example, you can use something like output_file=${2:-logfile}. If $2 is omitted and thus empty, output_file will be set to logfile. Arithmetic expansion: i=$(( (i + 1) % 5 )). Sequences: {1..10}. Trimming of strings: ${var%suffix} and ${var#prefix}. For example if var=foo.pdf, then echo ${var%.pdf}.txt prints foo.txt.
  • Brace expansion using {...} can reduce having to re-type similar text and automate combinations of items. This is helpful in examples like mv foo.{txt,pdf} some-dir (which moves both files), cp somefile{,.bak} (which expands to cp somefile somefile.bak) or mkdir -p test-{a,b,c}/subtest-{1,2,3} (which expands all possible combinations and creates a directory tree).
  • The output of a command can be treated like a file via <(some command). For example, compare local /etc/hostswith a remote one:
      diff /etc/hosts <(ssh somehost cat /etc/hosts)
  • When writing scripts you may want to put all of your code in curly braces. If the closing brace is missing, your script will be prevented from executing due to a syntax error. This makes sense when your script is going to be downloaded from the web, since it prevents partially downloaded scripts from executing:
      # Your code here
  • Know about "here documents" in Bash, as in cat <<EOF ....
  • In Bash, redirect both standard output and standard error via: some-command >logfile 2>&1 or some-command &>logfile. Often, to ensure a command does not leave an open file handle to standard input, tying it to the terminal you are in, it is also good practice to add </dev/null.
  • Use man ascii for a good ASCII table, with hex and decimal values. For general encoding info, man unicodeman utf-8, and man latin1 are helpful.
  • Use screen or tmux to multiplex the screen, especially useful on remote ssh sessions and to detach and re-attach to a session. byobu can enhance screen or tmux providing more information and easier management. A more minimal alternative for session persistence only is dtach.
  • In ssh, knowing how to port tunnel with -L or -D (and occasionally -R) is useful, e.g. to access web sites from a remote server.
  • It can be useful to make a few optimizations to your ssh configuration; for example, this ~/.ssh/config contains settings to avoid dropped connections in certain network environments, uses compression (which is helpful with scp over low-bandwidth connections), and multiplex channels to the same server with a local control file:
      ControlMaster auto
      ControlPath /tmp/%r@%h:%p
      ControlPersist yes
  • A few other options relevant to ssh are security sensitive and should be enabled with care, e.g. per subnet or host or in trusted networks: StrictHostKeyChecking=noForwardAgent=yes
  • Consider mosh an alternative to ssh that uses UDP, avoiding dropped connections and adding convenience on the road (requires server-side setup).
  • To get the permissions on a file in octal form, which is useful for system configuration but not available in ls and easy to bungle, use something like
      stat -c '%A %a %n' /etc/timezone
  • For interactive selection of values from the output of another command, use percol or fzf.
  • For interaction with files based on the output of another command (like git), use fpp (PathPicker).
  • For a simple web server for all files in the current directory (and subdirs), available to anyone on your network, use:python -m SimpleHTTPServer 7777 (for port 7777 and Python 2) and python -m http.server 7777 (for port 7777 and Python 3).
  • For running a command as another user, use sudo. Defaults to running as root; use -u to specify another user. Use -i to login as that user (you will be asked for your password).
  • For switching the shell to another user, use su username or su - username. Include the - to get an environment as if the user just logged in. Omitting the username defaults to root. You will be asked for the password of the user you are switching to.
  • Know about the 128K limit on command lines. This "Argument list too long" error is common when wildcard matching large numbers of files. (When this happens alternatives like find and xargs may help.)
  • For a basic calculator (and of course access to Python in general), use the python interpreter. For example,
>>> 2+3

Processing files and data

  • To locate a file by name in the current directory, find . -iname '*something*' (or similar). To find a file anywhere by name, use locate something (but bear in mind updatedb may not have indexed recently created files).
  • For general searching through source or data files (more advanced than grep -r), use ag.
  • To convert HTML to text: lynx -dump -stdin
  • For Markdown, HTML, and all kinds of document conversion, try pandoc.
  • If you must handle XML, xmlstarlet is old but good.
  • For JSON, use jq.
  • For YAML, use shyaml.
  • For Excel or CSV files, csvkit provides in2csvcsvcutcsvjoincsvgrep, etc.
  • For Amazon S3, s3cmd is convenient and s4cmd is faster. Amazon's aws and the improved saws are essential for other AWS-related tasks.
  • Know about sort and uniq, including uniq's -u and -d options -- see one-liners below. See also comm.
  • Know about cutpaste, and join to manipulate text files. Many people use cut but forget about join.
  • Know about wc to count newlines (-l), characters (-m), words (-w) and bytes (-c).
  • Know about tee to copy from stdin to a file and also to stdout, as in ls -al | tee file.txt.
  • For more complex calculations, including grouping, reversing fields, and statistical calculations, consider datamash.
  • Know that locale affects a lot of command line tools in subtle ways, including sorting order (collation) and performance. Most Linux installations will set LANG or other locale variables to a local setting like US English. But be aware sorting will change if you change locale. And know i18n routines can make sort or other commands run many times slower. In some situations (such as the set operations or uniqueness operations below) you can safely ignore slow i18n routines entirely and use traditional byte-based sort order, using export LC_ALL=C.
  • You can set a specific command's environment by prefixing its invocation with the environment variable settings, as in TZ=Pacific/Fiji date.
  • Know basic awk and sed for simple data munging. For example, summing all numbers in the third column of a text file: awk '{ x += $3 } END { print x }'. This is probably 3X faster and 3X shorter than equivalent Python.
  • To replace all occurrences of a string in place, in one or more files:
      perl -pi.bak -e 's/old-string/new-string/g' my-files-*.txt
  • To rename multiple files and/or search and replace within files, try repren. (In some cases the rename command also allows multiple renames, but be careful as its functionality is not the same on all Linux distributions.)
      # Full rename of filenames, directories, and contents foo -> bar:
      repren --full --preserve-case --from foo --to bar .
      # Recover backup files whatever.bak -> whatever:
      repren --renames --from '(.*)\.bak' --to '\1' *.bak
      # Same as above, using rename, if available:
      rename 's/\.bak$//' *.bak
  • As the man page says, rsync really is a fast and extraordinarily versatile file copying tool. It's known for synchronizing between machines but is equally useful locally. When security restrictions allow, using rsync instead of scp allows recovery of a transfer without restarting from scratch. It also is among the fastest ways to delete large numbers of files:
mkdir empty && rsync -r --delete empty/ some-dir && rmdir some-dir
  • Use shuf to shuffle or select random lines from a file.
  • Know sort's options. For numbers, use -n, or -h for handling human-readable numbers (e.g. from du -h). Know how keys work (-t and -k). In particular, watch out that you need to write -k1,1 to sort by only the first field; -k1 means sort according to the whole line. Stable sort (sort -s) can be useful. For example, to sort first by field 2, then secondarily by field 1, you can use sort -k1,1 | sort -s -k2,2.
  • If you ever need to write a tab literal in a command line in Bash (e.g. for the -t argument to sort), press ctrl-v [Tab] or write $'\t' (the latter is better as you can copy/paste it).
  • The standard tools for patching source code are diff and patch. See also diffstat for summary statistics of a diff and sdiff for a side-by-side diff. Note diff -r works for entire directories. Use diff -r tree1 tree2 | diffstat for a summary of changes. Use vimdiff to compare and edit files.
  • For binary files, use hdhexdump or xxd for simple hex dumps and bvi or biew for binary editing.
  • Also for binary files, strings (plus grep, etc.) lets you find bits of text.
  • For binary diffs (delta compression), use xdelta3.
  • To convert text encodings, try iconv. Or uconv for more advanced use; it supports some advanced Unicode things. For example, this command lowercases and removes all accents (by expanding and dropping them):
      uconv -f utf-8 -t utf-8 -x '::Any-Lower; ::Any-NFD; [:Nonspacing Mark:] >; ::Any-NFC; ' < input.txt > output.txt
  • To split files into pieces, see split (to split by size) and csplit (to split by a pattern).
  • To manipulate date and time expressions, use dateadddatediffstrptime etc. from dateutils.
  • Use zlesszmorezcat, and zgrep to operate on compressed files.
  • File attributes are settable via chattr and offer a lower-level alternative to file permissions. For example, to protect against accidental file deletion the immutable flag:  sudo chattr +i /critical/directory/or/file
  • Use getfacl and setfacl to save and restore file permissions. For example:
   getfacl -R /some/path > permissions.txt
   setfacl --restore=permissions.txt

System debugging

  • For web debugging, curl and curl -I are handy, or their wget equivalents, or the more modern httpie.
  • To know current cpu/disk status, the classic tools are top (or the better htop), iostat, and iotop. Use iostat -mxz 15 for basic CPU and detailed per-partition disk stats and performance insight.
  • For network connection details, use netstat and ss.
  • For a quick overview of what's happening on a system, dstat is especially useful. For broadest overview with details, use glances.
  • To know memory status, run and understand the output of free and vmstat. In particular, be aware the "cached" value is memory held by the Linux kernel as file cache, so effectively counts toward the "free" value.
  • Java system debugging is a different kettle of fish, but a simple trick on Oracle's and some other JVMs is that you can run kill -3 <pid> and a full stack trace and heap summary (including generational garbage collection details, which can be highly informative) will be dumped to stderr/logs. The JDK's jpsjstatjstackjmap are useful. SJK tools are more advanced.
  • Use mtr as a better traceroute, to identify network issues.
  • For looking at why a disk is full, ncdu saves time over the usual commands like du -sh *.
  • To find which socket or process is using bandwidth, try iftop or nethogs.
  • The ab tool (comes with Apache) is helpful for quick-and-dirty checking of web server performance. For more complex load testing, try siege.
  • For more serious network debugging, wiresharktshark, or ngrep.
  • Know about strace and ltrace. These can be helpful if a program is failing, hanging, or crashing, and you don't know why, or if you want to get a general idea of performance. Note the profiling option (-c), and the ability to attach to a running process (-p).
  • Know about ldd to check shared libraries etc.
  • Know how to connect to a running process with gdb and get its stack traces.
  • Use /proc. It's amazingly helpful sometimes when debugging live problems. Examples: /proc/cpuinfo/proc/meminfo/proc/cmdline/proc/xxx/cwd/proc/xxx/exe/proc/xxx/fd//proc/xxx/smaps (where xxx is the process id or pid).
  • When debugging why something went wrong in the past, sar can be very helpful. It shows historic statistics on CPU, memory, network, etc.
  • For deeper systems and performance analyses, look at stap (SystemTap), perf, and sysdig.
  • Check what OS you're on with uname or uname -a (general Unix/kernel info) or lsb_release -a (Linux distro info).
  • Use dmesg whenever something's acting really funny (it could be hardware or driver issues).
  • If you delete a file and it doesn't free up expected disk space as reported by du, check whether the file is in use by a process: lsof | grep deleted | grep "filename-of-my-big-file"


A few examples of piecing together commands:
  • It is remarkably helpful sometimes that you can do set intersection, union, and difference of text files via sort/uniq. Suppose a and b are text files that are already uniqued. This is fast, and works on files of arbitrary size, up to many gigabytes. (Sort is not limited by memory, though you may need to use the -T option if /tmp is on a small root partition.) See also the note about LC_ALL above and sort's -u option (left out for clarity below).
      cat a b | sort | uniq > c   # c is a union b
      cat a b | sort | uniq -d > c   # c is a intersect b
      cat a b b | sort | uniq -u > c   # c is set difference a - b
  • Use grep . * to quickly examine the contents of all files in a directory (so each line is paired with the filename), or head -100 * (so each file has a heading). This can be useful for directories filled with config settings like those in /sys/proc/etc.
  • Summing all numbers in the third column of a text file (this is probably 3X faster and 3X less code than equivalent Python):
      awk '{ x += $3 } END { print x }' myfile
  • To see sizes/dates on a tree of files, this is like a recursive ls -l but is easier to read than ls -lR:
      find . -type f -ls
  • Say you have a text file, like a web server log, and a certain value that appears on some lines, such as an acct_idparameter that is present in the URL. If you want a tally of how many requests for each acct_id:
      cat access.log | egrep -o 'acct_id=[0-9]+' | cut -d= -f2 | sort | uniq -c | sort -rn
  • To continuously monitor changes, use watch, e.g. check changes to files in a directory with watch -d -n 2 'ls -rtlh | tail' or to network settings while troubleshooting your wifi settings with watch -d -n 2 ifconfig.
  • Run this function to get a random tip from this document (parses Markdown and extracts an item):
      function taocl() {
        curl -s |
          pandoc -f markdown -t html |
          xmlstarlet fo --html --dropdtd |
          xmlstarlet sel -t -v "(html/body/ul/li[count(p)>0])[$RANDOM mod last()+1]" |
          xmlstarlet unesc | fmt -80

Obscure but useful

  • expr: perform arithmetic or boolean operations or evaluate regular expressions
  • m4: simple macro processor
  • yes: print a string a lot
  • cal: nice calendar
  • env: run a command (useful in scripts)
  • printenv: print out environment variables (useful in debugging and scripts)
  • look: find English words (or lines in a file) beginning with a string
  • cutpaste and join: data manipulation
  • fmt: format text paragraphs
  • pr: format text into pages/columns
  • fold: wrap lines of text
  • column: format text fields into aligned, fixed-width columns or tables
  • expand and unexpand: convert between tabs and spaces
  • nl: add line numbers
  • seq: print numbers
  • bc: calculator
  • factor: factor integers
  • gpg: encrypt and sign files
  • toe: table of terminfo entries
  • nc: network debugging and data transfer
  • socat: socket relay and tcp port forwarder (similar to netcat)
  • slurm: network traffic visualization
  • dd: moving data between files or devices
  • file: identify type of a file
  • tree: display directories and subdirectories as a nesting tree; like ls but recursive
  • stat: file info
  • time: execute and time a command
  • timeout: execute a command for specified amount of time and stop the process when the specified amount of time completes.
  • lockfile: create semaphore file that can only be removed by rm -f
  • logrotate: rotate, compress and mail logs.
  • watch: run a command repeatedly, showing results and/or highlighting changes
  • tac: print files in reverse
  • shuf: random selection of lines from a file
  • comm: compare sorted files line by line
  • pv: monitor the progress of data through a pipe
  • hdhexdumpxxdbiew and bvi: dump or edit binary files
  • strings: extract text from binary files
  • tr: character translation or manipulation
  • iconv or uconv: conversion for text encodings
  • split and csplit: splitting files
  • sponge: read all input before writing it, useful for reading from then writing to the same file, e.g., grep -v something some-file | sponge some-file
  • units: unit conversions and calculations; converts furlongs per fortnight to twips per blink (see also /usr/share/units/definitions.units)
  • apg: generates random passwords
  • xz: high-ratio file compression
  • ldd: dynamic library info
  • nm: symbols from object files
  • ab: benchmarking web servers
  • strace: system call debugging
  • mtr: better traceroute for network debugging
  • cssh: visual concurrent shell
  • rsync: sync files and folders over SSH or in local file system
  • wireshark and tshark: packet capture and network debugging
  • ngrep: grep for the network layer
  • host and dig: DNS lookups
  • lsof: process file descriptor and socket info
  • dstat: useful system stats
  • glances: high level, multi-subsystem overview
  • iostat: Disk usage stats
  • mpstat: CPU usage stats
  • vmstat: Memory usage stats
  • htop: improved version of top
  • last: login history
  • w: who's logged on
  • id: user/group identity info
  • sar: historic system stats
  • iftop or nethogs: network utilization by socket or process
  • ss: socket statistics
  • dmesg: boot and system error messages
  • sysctl: view and configure Linux kernel parameters at run time
  • hdparm: SATA/ATA disk manipulation/performance
  • lsblk: list block devices: a tree view of your disks and disk partitions
  • lshwlscpulspcilsusbdmidecode: hardware information, including CPU, BIOS, RAID, graphics, devices, etc.
  • lsmod and modinfo: List and show details of kernel modules.
  • fortuneddate, and sl: um, well, it depends on whether you consider steam locomotives and Zippy quotations "useful"

OS X only

These are items relevant only on OS X.
  • Package management with brew (Homebrew) and/or port (MacPorts). These can be used to install on OS X many of the above commands.
  • Copy output of any command to a desktop app with pbcopy and paste input from one with pbpaste.
  • To enable the Option key in OS X Terminal as an alt key (such as used in the commands above like alt-balt-f, etc.), open Preferences -> Profiles -> Keyboard and select "Use Option as Meta key".
  • To open a file with a desktop app, use open or open -a /Applications/
  • Spotlight: Search files with mdfind and list metadata (such as photo EXIF info) with mdls.
  • Be aware OS X is based on BSD Unix, and many commands (for example pslstailawksed) have many subtle variations from Linux, which is largely influenced by System V-style Unix and GNU tools. You can often tell the difference by noting a man page has the heading "BSD General Commands Manual." In some cases GNU versions can be installed, too (such as gawk and gsed for GNU awk and sed). If writing cross-platform Bash scripts, avoid such commands (for example, consider Python or perl) or test carefully.
  • To get OS X release information, use sw_vers.

Windows only

These items are relevant only on Windows.
  • On Windows 10, you can use Bash on Ubuntu on Windows, which provides a familiar Bash environment with Unix command line utilities. On the plus side, this allows Linux programs to run on Windows. On the other hand this does not support the running of Windows programs from the Bash prompt.
  • Access the power of the Unix shell under Microsoft Windows by installing Cygwin. Most of the things described in this document will work out of the box.
  • Install additional Unix programs with the Cygwin's package manager.
  • Use mintty as your command-line window.
  • Access the Windows clipboard through /dev/clipboard.
  • Run cygstart to open an arbitrary file through its registered application.
  • Access the Windows registry with regtool.
  • Note that a C:\ Windows drive path becomes /cygdrive/c under Cygwin, and that Cygwin's / appears under C:\cygwin on Windows. Convert between Cygwin and Windows-style file paths with cygpath. This is most useful in scripts that invoke Windows programs.
  • You can perform and script most Windows system administration tasks from the command line by learning and using wmic.
  • Another option to get Unix look and feel under Windows is Cash. Note that only very few Unix commands and command-line options are available in this environment.
  • An alternative option to get GNU developer tools (such as GCC) on Windows is MinGW and its MSYS package, which provides utilities such as bash, gawk, make and grep. MSYS doesn't have all the features compared to Cygwin. MinGW is particularly useful for creating native Windows ports of Unix tools.

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