Shortcuts and History

• Ctrl + A — move to beginning of line

• Ctrl + B — moves backward one character

• Ctrl + C — halts the current command

• Ctrl + D — deletes one character backward or logs out of current session, similar to exit

• Ctrl + E — moves to end of line

• Ctrl + F — moves forward one character

• Ctrl + G — aborts the current editing command and ring the terminal bell

• Ctrl + H — deletes one character under cursor (same as DELETE)

• Ctrl + J — same as RETURN

• Ctrl + K — deletes (kill) forward to end of line

• Ctrl + L — clears screen and redisplay the line

• Ctrl + M — same as RETURN

• Ctrl + N — next line in command history

• Ctrl + O — same as RETURN, then displays next line in history file

• Ctrl + P — previous line in command history

• Ctrl + Q — resumes suspended shell output

• Ctrl + R — searches backward

• Ctrl + S — searches forward or suspends shell output

• Ctrl + T — transposes two characters

• Ctrl + U — kills backward from point to the beginning of line

• Ctrl + V — makes the next character typed verbatim

• Ctrl + W — kills the word behind the cursor

• Ctrl + X — lists the possible filename completions of the current word

• Ctrl + Y — retrieves (yank) last item killed

• Ctrl + Z — stops the current command, resume with fg in the foreground or bg in the background

• Alt + B — moves backward one word

• Alt + D — deletes next word

• Alt + F — moves forward one word

• Alt + H — deletes one character backward

• Alt + T — transposes two words

• Alt + . — pastes last word from the last command. Pressing it repeatedly traverses through command history.

• Alt + U — capitalizes every character from the current cursor position to the end of the word

• Alt + L — uncapitalizes every character from the current cursor position to the end of the word

• Alt + C — capitalizes the letter under the cursor. The cursor then moves to the end of the word.

• Alt + R — reverts any changes to a command you’ve pulled from your history if you’ve edited it.

• Alt + ? — list possible completions to what is typed

• Alt + ^ — expand line to most recent match from history

• Ctrl + X then ( — start recording a keyboard macro

• Ctrl + X then ) — finish recording keyboard macro

• Ctrl + X then E — recall last recorded keyboard macro

• Ctrl + X then Ctrl + E — invoke text editor (specified by $EDITOR) on current command line then execute results as shell commands

• Ctrl + A then D — logout from screen but don't kill it, if any command exist, it will continue

• BACKSPACE — deletes one character backward

• DELETE — deletes one character under cursor

• history — shows command line history

• !! — repeats the last command

• !<n> — refers to command line 'n'

• !<string> — refers to command starting with 'string'

• esc :wq — exits and saves script

• exit — logs out of current session

Bash Basics

• env — displays all environment variables
• echo $SHELL — displays the shell you're using
• echo $BASH_VERSION — displays bash version
• bash — if you want to use bash (type exit to go back to your previously opened shell)
• whereis bash — locates the binary, source and manual-page for a command
• which bash — finds out which program is executed as 'bash' (default: /bin/bash, can change across environments)
• clear — clears content on window (hide displayed lines)

File Commands

• ls — lists your files in current directory, ls <dir> to print files in a specific directory
• ls -l — lists your files in 'long format', which contains the exact size of the file, who owns the file and who has the right to look at it, and when it was last modified
• ls -a — lists all files in 'long format', including hidden files (name beginning with '.')
• ln -s <filename> <link> — creates symbolic link to file
• readlink <filename> — shows where a symbolic links points to
• tree — show directories and subdirectories in easily readable file tree
• mc — terminal file explorer (alternative to ncdu)
• touch <filename> — creates or updates (edit) your file
• mktemp -t <filename> — make a temp file in /tmp/ which is deleted at next boot (-d to make directory)
• cat <filename> — displays file raw content (will not be interpreted)
• cat -n <filename> — shows number of lines
• nl <file.sh> — shows number of lines in file
• cat filename1 > filename2 — Copy filename1 to filename2
• cat filename1 >> filename2 — merge two files texts together
• any_command > <filename> — '>' is used to perform redirections, it will set any_command's stdout to file instead of "real stdout" (generally /dev/stdout)
• more <filename> — shows the first part of a file (move with space and type q to quit)
• head <filename> — outputs the first lines of file (default: 10 lines)
• tail <filename> — outputs the last lines of file (useful with -f option) (default: 10 lines)
• vim <filename> — opens a file in VIM (VI iMproved) text editor, will create it if it doesn't exist
• mv <filename1> <dest> — moves a file to destination, behavior will change based on 'dest' type (dir: file is placed into dir; file: file will replace dest (tip: useful for renaming))
• cp <filename1> <dest> — copies a file
• rm <filename> — removes a file
• find . -name <name> <type> — searches for a file or a directory in the current directory and all its sub-directories by its name
• diff <filename1> <filename2> — compares files, and shows where they differ
• wc <filename> — tells you how many lines, words and characters there are in a file. Use -lwc (lines, word, character) to output only 1 of those informations
• sort <filename> — sorts the contents of a text file line by line in alphabetical order, use -n for numeric sort and -r for reversing order.
• sort -t -k <filename> — sorts the contents on specific sort key field starting from 1, using the field separator t.
• rev — reverse string characters (hello becomes olleh)
• chmod -options <filename> — lets you change the read, write, and execute permissions on your files (more infos: SUID, GUID)
• gzip <filename> — compresses files using gzip algorithm
• gunzip <filename> — uncompresses files compressed by gzip
• gzcat <filename> — lets you look at gzipped file without actually having to gunzip it
• lpr <filename> — prints the file
• lpq — checks out the printer queue
• lprm <jobnumber> — removes something from the printer queue
• genscript — converts plain text files into postscript for printing and gives you some options for formatting
• dvips <filename> — prints .dvi files (i.e. files produced by LaTeX)
• grep <pattern> <filenames> — looks for the string in the files
• grep -r <pattern> <dir> — search recursively for pattern in directory
• head -n file_name | tail +n — Print nth line from file.
• head -y lines.txt | tail +x — want to display all the lines from x to y. This includes the xth and yth lines.
• sed 's/<pattern>/<replacement>/g' <filename> — replace pattern in file with replacement value to std output the character after s (/) is the delimiter
• sed -i 's/<pattern>/<replacement>/g' <filename> — replace pattern in file with replacement value in place
• echo "this" | sed 's/is/at/g' — replace pattern from input stream with replacement value

Directory Commands

• mkdir <dirname> — makes a new directory
• rmdir <dirname> — remove an empty directory
• rmdir -rf <dirname> — remove a non-empty directory
• mv <dir1> <dir2> — rename a directory from <dir1> to <dir2>
• cd — changes to home
• cd .. — changes to the parent directory
• cd <dirname> — changes directory
• cp -r <dir1> <dir2> — copy <dir1> into <dir2> including sub-directories
• pwd — tells you where you currently are
• cd ~ — changes to home.
• cd - — changes to previous working directory

SSH, System Info and Network Commands

• ssh user@host — connects to host as user
• ssh -p <port> user@host — connects to host on specified port as user
• ssh-copy-id user@host — adds your ssh key to host for user to enable a keyed or passwordless login
• whoami — returns your username
• su <user> — switch to a different user
• su - — switch to root, likely needs to be sudo su -
• sudo <command> — execute command as the root user
• passwd — lets you change your password
• quota -v — shows what your disk quota is
• date — shows the current date and time
• cal — shows the month's calendar
• uptime — shows current uptime
• w — displays who is online
• finger <user> — displays information about user
• uname -a — shows kernel information
• man <command> — shows the manual for specified command
• info <command> — shows another documentation system for the specific command
• help — shows documentation about built-in commands and functions
• df — shows disk usage
• du <filename> — shows the disk usage of the files and directories in filename (du -s give only a total)
• resize2fs — ext2/ext3/ext4 file system resizer
• last <yourUsername> — lists your last logins
• ps -u yourusername — lists your processes
• kill <PID> — kills the processes with the ID you gave
• killall <processname> — kill all processes with the name
• top — displays your currently active processes
• lsof — lists open files
• bg — lists stopped or background jobs ; resume a stopped job in the background
• fg — brings the most recent job in the foreground
• fg <job> — brings job to the foreground
• ping <host> — pings host and outputs results
• whois <domain> — gets whois information for domain
• dig <domain> — gets DNS information for domain
• dig -x <host> — reverses lookup host
• wget <file> — downloads file
• netstat — Print network connections, routing tables, interface statistics, masquerade connections, and multicast memberships
• time <command> — report time consumed by command execution

Variables

• varname=value — defines a variable

• varname=value command — defines a variable to be in the environment of a particular subprocess

• echo $varname — checks a variable's value

• echo $$ — prints process ID of the current shell

• echo $! — prints process ID of the most recently invoked background job

• echo $? — displays the exit status of the last command

• read <varname> — reads a string from the input and assigns it to a variable

• read -p "prompt" <varname> — same as above but outputs a prompt to ask user for value

• column -t <filename> — display info in pretty columns (often used with pipe)

• let <varname> = <equation> — performs mathematical calculation using operators like +, -, *, /, %

• export VARNAME=value — defines an environment variable (will be available in subprocesses)

• export -f <funcname> — Exports function 'funcname'

• export var1="var1 value" — Export and assign in the same statement

• export <varname> — Copy Bash variable

• declare -x <varname> — Copy Bash variable

• array[0]=valA — how to define an array

• array[1]=valB

• array[2]=valC

• array=([2]=valC [0]=valA [1]=valB) — another way

• array=(valA valB valC) — and another

• ${array[i]} — displays array's value for this index. If no index is supplied, array element 0 is assumed

• ${#array[i]} — to find out the length of any element in the array

• ${#array[@]} — to find out how many values there are in the array

• declare -a — the variables are treated as arrays

• declare -f — uses function names only

• declare -F — displays function names without definitions

• declare -i — the variables are treated as integers

• declare -r — makes the variables read-only

• declare -x — marks the variables for export via the environment

• declare -l — uppercase values in the variable are converted to lowercase

• declare -A — makes it an associative array

• ${varname:-word} — if varname exists and isn't null, return its value; otherwise return word

• ${varname:word} — if varname exists and isn't null, return its value; otherwise return word

• ${varname:=word} — if varname exists and isn't null, return its value; otherwise set it word and then return its value

• ${varname:?message} — if varname exists and isn't null, return its value; otherwise print varname, followed by message and abort the current command or script

• ${varname:+word} — if varname exists and isn't null, return word; otherwise return null

• ${varname:offset:length} — performs substring expansion. It returns the substring of $varname starting at offset and up to length characters

• ${variable#pattern} — if the pattern matches the beginning of the variable's value, delete the shortest part that matches and return the rest

• ${variable##pattern} — if the pattern matches the beginning of the variable's value, delete the longest part that matches and return the rest

• ${variable%pattern} — if the pattern matches the end of the variable's value, delete the shortest part that matches and return the rest

• ${variable%%pattern} — if the pattern matches the end of the variable's value, delete the longest part that matches and return the rest

• ${variable/pattern/string} — the longest match to pattern in variable is replaced by string. Only the first match is replaced

• ${variable//pattern/string} — the longest match to pattern in variable is replaced by string. All matches are replaced

• ${#varname} — returns the length of the value of the variable as a character string

• *(patternlist) — matches zero or more occurrences of the given patterns

• +(patternlist) — matches one or more occurrences of the given patterns

• ?(patternlist) — matches zero or one occurrence of the given patterns

• @(patternlist) — matches exactly one of the given patterns

• !(patternlist) — matches anything except one of the given patterns

• $(UNIX command) — command substitution: runs the command and returns standard output

• typeset -l <x> — makes variable local - <x> must be an integer

Functions

function functname() {
  shell commands
}