Cheatsheet

“UNIX is simple and coherent, but it takes a genius (or at any rate, a programmer) to understand and appreciate its simplicity.” — Dennis M. Ritchie

This page lists fundamental utilities and gives a short summary of their purpose:

Parts in black are as found in recent canonical implementations (GNU coreutils, util-linux, etc.).
Parts in blue are POSIX.2024, with links to the standard where appropriate. To maximize portability of your shell scripts, stick to the blue.
Heavy typeface indicates fixed parts of commands, e.g. command and option names.
Italic indicates variable parts of commands, e.g. option values and arguments.
Brackets denote [optional] parts (heavy brackets are regular text).
Alternatives are separated with a |
Parts which may repeat are suffixed with ...
Commentary is given in italic serif typeface.

Note: The utilities (both as standardized and as commonly implemented) typically support many more options than shown. Only canonical invocations and their most important related options are listed.

Unix Magic by Gary Overacre — By Gary Overacre. Copyright © 1986 Unitech Software.

Shell scripting

. fileexecute commands in current environment
: [ignored-arg...]null utility
bc [-l] [file...]arbitrary-precision arithmetic language
builtin [shell-builtin [arg...]]execute a shell built-in (suppress function lookup)
break [n]exit from for, while or until loop
cd [dir|-]change the working directory
command [-p] [cmd [arg...]]execute a simple command (suppresses function lookup)
command [-p] [-v|-V] cmdlook up a command
continuecontinue for, while or until loop
env [-i] [-S] [name=value]... [cmd [arg...]]execute a command with modified environment
envprint current environment
eval [arg...]construct command by concatenating arguments
exec [cmd [arg...]]perform redirections in current shell, or execute a utility
exit [n]cause the shell to exit
export name[=word]...set the export attribute of a variable
export [-p]print exported variables
falseexit with a non-zero exit code
getopts opt-string var-name [param...]
hash -rforget remembered utility paths
hash [utility]print remembered utility paths
pause [ignored-arg...]don't exit, efficiently
pwdprint the working directory
read [-r]¹ [-d delim] var...read from standard input into shell variables
readonly name[=word]...set the readonly attribute of a variable
readonly [-p]print readonly variables
return [n]return from a function or dot script
set [-eux] [+eux] [-o option] [+o option] [--] [arg...]set options and arguments
shift [n]shift positional parameters
sleep number[s|m|h|d]sleep for a given time interval
test [expr]
- where expr is:
  - ! exprnegation
  - -e pathpath exists
  - -d pathpath exists and is a directory
  - -f pathpath exists and is a regular file
  - -p pathpath exists and is a pipe
  - -s pathpath exists and is a file with size greater than zero
  - -n stringstring has non-zero length
  - -z stringstring has zero length
  - s1 = s2string s1 and s2 are identical
  - s1 != s2string s1 and s2 are not identical
  - s1 > s2string s1 collates after s2 (locale-aware)
  - s1 < s2string s1 collates before s2 (locale-aware)
  - n1 -eq n2integers n1 and n2 are equal
  - n1 -ne n2integers n1 and n2 are not equal
  - n1 -lt n2integer n1 is less than integer n2
  - n1 -le n2integer n1 is less than or equal to integer n2
  - n1 -gt n2integer n1 is greater than integer n2
  - n1 -ge n2integer n1 is greater than or equal to integer n2
[² expr ]same as test expr but more readable
timeout [-fp] [-k time] [-s signal] duration cmd [arg...]execute with a time limit
trap [action EXIT|signal...]trap signals
trueexit with a zero exit code
umask [-S] [mask]get or set the file mode creation mask
unset [-fv] name...unset variables and functions
wait [pid...]await process completion

Man pages

man [-k] [section] [name]display manual pages
apropos [expression]search manual page database (same as man -k)
whatis [expression]give a command summary (same as apropos -f, man -kf)

Text processing

Traditional

awk [-F sep] [-v var-assignment]... program [arg...]pattern scanning/processing language
awk [-F sep] -f program-file [-f program-file]... [-v var-assignment]... program [arg...]
cat [-v] [file...]concatenate files
comm [-123] [-z] file1 file2select or reject lines common to two files
cut [-d delimiter] [-f fields] [-z] [file...]select fields of input
date [-u] [-d date] [+format]output formatted date and time
- where the following format modifiers are recognized³:
  - +%dday (two digits)
  - +%mmonth (two digits)
  - +%yyear
  - +%Hhour (two digits)
  - +%Mminute (two digits)
  - +%Ssecond (two digits)
  - +%%literal %
- where the allowed values for date are³:
  - @unix-timestamp
  - yesterday
  - 'last Monday'
  - '14 days ago - 2 hours'
diff?
fold?
grep [-E|-F] [-iv] pattern [file...]print matching lines
grep [-E|-F] [-iv] -f pattern-file [-f pattern-file]... [-e pattern]... [file...]
grep [-E|-F] [-iv] -e pattern [-e pattern]... [-f pattern-file]... [file...]
iconv [-c] [-f from-enc [-t to-enc] [file...]convert between encodings
iconv [-c] [-f from-enc] -t to-enc] [file...]
iconv -llist supported source end destination encodings
join?
od [-A addr-base] [-j skip] [-N count] [-t format] [--endian=big|little] [file...]
- where the allowed values for addr-base are³:
  - ddecimal
  - ooctal
  - xhexadecimal
- where the allowed values for format are³:
  - -d[n]signed decimal, n bytes in a group
  - -o[n]octal, n bytes in a group
  - -u[n]unsigned decimal, n bytes in a group
  - -x[n]hexadecimal, n bytes in a group
paste [-d delimiters] [-s] [-z] [file...]merge corresponding lines of input
patch [-i patch-file] [-o output-file] [-p n] [-u] [file]apply a diff
printf format [arg...]write formatted output
- where the following format modifiers are recognized³:
  - %sstring
  - %ddecimal integer
  - %xhexadecimal integer
  - %ffloat
  - %%literal %
sed [-E] [-isuffix]⁴ [-n] [-z] script [file...]transform text on the fly
sed [-E] [-isuffix]⁴ [-n] [-z] -e script [-e script]... [-f script-file] [file...]
sed [-E] [-isuffix]⁴ [-n] [-z] -f script-file [-f script-file]... [-e script] [file...]
- where some example scripts are³:
  - s/pattern/replacement/replace occurrences of pattern with replacement
  - npprint n-th line
  - /pattern/,$ddelete lines between first occurrence of pattern and end of input
sort [-o output-file] [file...]
split [-a suffix-length] [-b n[unit]] [-l lines] [file [name]]split a file in parts
- without unit, defaults to bytes; valid unit is³:
  - kkiB
  - mMiB
  - K|M|G|etc.kibi-, mebi-, gibi-, ... bytes (IEC)
  - KB|MB|GB|etc.kilo-, mega-, giga-, ... bytes (SI)
strings [-n min-len] [-t offset-format] [file...]find printable strings
tee [-a] [-p] [file...]duplicate standard input
tr [-cds] string1 string2translate or delete characters
- where string1 and string2 may be³:
  - [a-z]characters between a and z (inclusive, no multibyte support)
  - [[:upper:]]uppercase characters (no multibyte support)
  - [[:lower:]]lowercase characters (no multibyte support)
  - [[:space:]]whitespace (no multibyte support)
  - [[:alnum:]]alphanumeric characters (no multibyte support)
uniq [-cdu] [-f skip] [-s skip] [-z] [file [output-file]]keep or remove duplicates
wc [-clmw] [-L] [file...]word count
xargs

Modern

base64 [-d] [file]encode or decode Base64 data
hexdump [-C] [-l length] [-s offset] [file...]display file in hexadecimal
seq [-f format] [-s separator] [-w] [first [step]] lastprint a sequence of numbers

Inspecting contents of the file system

Traditional

basename path [suffix]keep the last component of a path
basename [-s suffix] path...
df [-h] [--si] [file...]report free disk space
dirname path...strip the last component of a path
du [-as] [-bh] [--si] [file...]estimate file space usage
file [--mime-type] file...guess the file type
find [path...] [expression]search for files
- where the expressions are³:
  - ( expression )grouping
  - ! expressionnegation
  - expression [-a] expressionand (default)
  - expression -o expressionor
  - -deletedelete files and directories, implies -depth
  - -depthprocess files depth-first
  - -exec cmd [arg...] \; execute cmd for each file found
  - -executableby current user
  - -group nameowner by group with the given name (or gid)
  - -maxdepth n, -mindepth nlimit search depth
  - -name pattern, -iname patternname matches pattern (case insensitive)
  - -path pattern, -ipath patternpath matches pattern (case insensitive)
  - -print?
  - -print0?
  - -prunereject a subtree
  - -readableby current user
  - -sizesize of the file is³:
    - n[units]exactly n units:
      - 512-byte blocks if units not given
      - cbytes
      - kkibibytes (kiB)
      - Mmebibytes (MiB)
      - Ggibibytes (GiB)
    - +n[units]greater than (<) n units, units as above
    - -n[units]smaller than (>) n units, units as above
  - -type type, -type typesfile type is:
    - bblock special file
    - ccharacter special file
    - ddirectory
    - lsymbolic link
    - pnamed pipe
    - fregular file
    - ssocket
  - -user nameowner by user with the given name (or uid)
  - -writableby current user
ls [-ailrt] [-A] [--sort=by] [file...]list files
realpath [-e] [-m] [--relative-to=dir] file...resolve a path
readlink file...display the contents of a symbolic link
stat [-c format] file...display file status
sha256sum [file...], sha512sum [file...]calculate a checksum

Modern

btrfs filesystem du [-s] [--si] file...calculate disk usage for a file in Btrfs
tree [-L levels] [dir...]print a directory tree

Modifying contents of the file system

Traditional

chgrp [-R] [-c] [--reference=file] group file... change group ownership
chmod [-R] [-c] [--reference=file] mode file...change file mode
chown [-R] [-c] [--reference=file] owner[:group] file...change ownership
dd
ln [-sf] [-rT] source target create links
ln [-sf] [-rT] source... target-dir
mkdir [-p] [-m mode] dir...make directories
mkfifo [-m mode] name...create a named pipe
mv [-f] source targetmove or rename files
mv [-f] source... target-dir
rm -f [-rv] [file...]
rm -f [-rv] [file...]remove files or directories
rmdir [-p] dir...remove empty directories
touch [-acm] [-d datetime] [-r reference] [-t time] file...modify file timestamps

Modern

fallocate [-l length] [-n] filechange space allocation of a file
fallocate [-d] [-n] filedig holes in a file
mknod name b|c major minorcreate a block or character special file
truncate [-c] [-s size] file...grow or shrink files

Block devices

lsblk [-bfJln] [-o output-list] [device...]list block devices
lsblk -Hlist available columns (for use with -o)
mkfs.fstype [fstype-args...] device [fstype-args...]create a file system
mount [-t type]list mounted file systems
mount [-o options] [-t type] device mountpointmount a file system
mount --bind|--rbind|--move old-dir new-dirremount part of file hierarchy

Account and privilege control

chsh?
doas?
id [user]
id -G [-n] [user]
id -g [-rn] [user]
id -u [-rn] [user]
last?
lastlog?
newgrp [group]change to a new group
passwd?
su?
sudo?
who [-abu]display who is on the system

Process management

Traditional

fuser [-u] file...
kill...
nice...
ps...
renice...

Modern

htop?
killall?
pgrep?
pkill?

systemd

Service management

systemctl [--user] [list-units] [--failed] [pattern...]
systemctl [--user] status
systemctl [--user] status [pattern...]
systemctl [--user] start pattern?
systemctl [--user] stop pattern?
systemctl [--user] restart pattern?
systemctl [--user] reload pattern?
systemctl [--user] enable [--now] unit?
systemctl [--user] disable [--now] unit?
systemctl [--user] list-timers
systemctl [--user] edit unit?
systemctl [--user] daemon-reload
systemctl [--user] kill [--kill-whom=whom] [--signal=signal] pattern?

Logs

journalctl [--user] [-u unit] [-b boot] [-e] [-f] [-n n]
journalctl [--user] --list-bootsfor use with the -b option
journalctl [--user] --disk-usage
journalctl [--user] --vacuum-size=nM|Gdelete oldest logs to fit size limit
journalctl [--user] --vacuum-time=ndaysdelete logs older than n days

System

hostname?
uname?
reboot?
poweroff?
dmesg?
lsmod?
modprobe?
free?
iotop?
sysctl?

Misc

gdb?
less [-R] file?
strace?
stty?
time?
watch [-d] [-n fractional-seconds] cmd [arg...]refresh command output regularly

9 times out of 10, you want to use -r. ↩
The brackets [ ... ] do not designate an optional expr. These are literal brackets. This isn't special syntax, you actually are invoking a program called [ and the balancing right bracket ] is the last argument to the command. And yes, there is a /bin/[! ↩
These are just hand-picked examples which are most frequently used in practice. There's much more, read the standard and/or man page. ↩ ↩² ↩³ ↩⁴ ↩⁵ ↩⁶ ↩⁷ ↩⁸ ↩⁹ ↩¹⁰
Only suitable for interactive use, poorly portable even among implementations which support the option, see here. ↩ ↩² ↩³