Linux/Basic commands

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Unix-like operating systems require a working knowledge of several basic commands. Unix®, Linux, BSD and such use a ubiquitous set of these based on the Single UNIX Specification and other standards. Learning to operate a command line interface is a key skill in learning Linux and BSD.

Commands where mistyping could have inconvenient consequences should be drafted in a text editor first and then pasted into terminal, or after a # hash character for temporarily marking the text of the command as a non-executable comment, which is then removed after typing the correct command. Terminal emulators may support marking commands as comment in history through Ctrl+Alt+#.

Basic commands[edit | edit source]

IEEE Std 1003.1-2001 utilities
Name Category Description First appeared
admin SCCS Create and administer SCCS files
alias Misc Define or display aliases
ar Misc Create and maintain library archives
asa Text Processing Interpret carriage-control characters
at Process Management Execute commands at a later time Version 7 AT&T UNIX
awk Text processing Pattern scanning and processing language Version 7 AT&T UNIX
basename Filesystem Return non-directory portion of a pathname
bash Shell The Bourne-again shell
batch Process Management Schedule commands to be executed in a batch queue
bc Misc Arbitrary-precision arithmetic language
bg Process Management Run jobs in the background
break Shell programming Exit from for, while, or until loop
c99 C Programming Compile standard C programs
cal Misc Print a calendar Version 5 AT&T UNIX
cat Filesystem Concatenate and print files Version 1 AT&T UNIX
cd Filesystem Change the working directory
cflow C Programming Generate a C-language flowgraph
chgrp Filesystem Change the file group ownership
chmod Filesystem Change the file modes/attributes/permissions Version 1 AT&T UNIX
chown Filesystem Change the file ownership Version 1 AT&T UNIX
chroot Processes run a command or interactive shell using a specific directory as the root directory Prior to 4.2BSD
cksum Filesystem Write file checksums and sizes 4.4BSD
cmp Filesystem Compare two files Version 1 AT&T UNIX
comm Text Processing Select or reject lines common to two files Version 4 AT&T UNIX
command Shell Programming Execute a simple command
compress Filesystem Compress data 4.3BSD
continue Shell programming Continue for, while, or until loop
cp Filesystem Copy files Version 1 AT&T UNIX
crontab Misc Schedule periodic background work
csplit Text Processing Split files based on context PWB UNIX
ctags C Programming Create a tags file 3.0BSD
cut Shell Programming Cut out selected fields of each line of a file
cxref C Programming Generate a C-language program cross-reference table
date Misc Write the date and time Version 1 AT&T UNIX
dd Filesystem Convert and copy a file
delta SCCS Make a delta (change) to an SCCS file
df Filesystem Report free disk space Version 1 AT&T UNIX
diff Text processing Compare two files
dirname Filesystem Return the directory portion of a pathname
dot Shell programming Execute commands in the current environment
du Filesystem Estimate file space usage Version 1 AT&T UNIX
echo Shell programming Write arguments to standard output
ed Text processing The standard text editor Version 1 AT&T UNIX
env Misc list environment variables or invoke a command in a modified environment
eval Shell programming Construct command by concatenating arguments
ex Text processing Text editor BSD
exec Shell programming Execute commands and open, close, or copy file descriptors
exit Shell programming Cause the shell to exit
expand Text Processing Convert tabs to spaces 3.0BSD
export Misc Set the export attribute for variables
expr Shell Programming Evaluate arguments as an expression
false Shell programming Return false value
fc Misc Process the command history list
fg Process Management Run jobs in the foreground
file Filesystem Determine file type Version 4 AT&T UNIX
find Filesystem Find files Version 1 AT&T UNIX
flex C Programming Generate programs for lexical tasks
fold Text processing Filter for folding lines
fort77 C Programming w:FORTRAN compiler
fortune Misc Displays a random quotation
ftp Internet Internet file transfer program
fuser Process Management List process IDs of all processes that have one or more files open
gawk Text processing Pattern scanning and processing language, GNU's version of awk
gencat Misc Generate a formatted message catalog
get SCCS Get a version of an SCCS file
getconf Misc Get configuration values
getopts Shell Programming Parse utility options
grep Misc Search text for a pattern
groups Misc List groups a user belongs to
hash Misc Remember or report utility locations
head Text processing Copy the first part of files PWB UNIX
hostname Networking Show the system's host name
iconv Text processing Codeset conversion
id Misc Return user identity 4.4BSD
iostat Input/Output information collect and show operating system storage input and output statistics
ipcrm Misc Remove a message queue, semaphore set, or shared memory segment identifier
ipcs Misc Report interprocess communication facilities status
jobs Process Management Display status of jobs in the current session
join Text Processing Relational database operator
kill Process Management Terminate or signal processes Version 3 AT&T UNIX
less Text processing Display files on a page-by-page basis
lex C Programming Generate programs for lexical tasks
link Filesystem Call link function Version 1 AT&T UNIX
ln Filesystem Link files Version 1 AT&T UNIX
locale Misc Get locale-specific information
localedef Misc Define locale environment
logger Shell programming Log messages
login Misc Begin sessions on a system
logname Misc Return the user's login name 4.4BSD
logout Misc End sessions on a system
lp Text Processing Send files to a printer
ls Filesystem List directory contents Version 1 AT&T UNIX
m4 Misc Macro processor PWB UNIX
mailx Misc Process messages Version 1 AT&T UNIX
make Programming Maintain, update, and regenerate groups of programs
man Misc Display system documentation
mesg Misc Permit or deny messages Version 1 AT&T UNIX
mkdir Filesystem Make directories Version 1 AT&T UNIX
mkfifo Filesystem Make FIFO special files 4.4BSD
mktemp Filesystem Create a temporary file or directory
more Text processing Display files on a page-by-page basis
mount Filesystem Mount a file system
mv Filesystem Move files Version 1 AT&T UNIX
nano Text Programming Small text editor
netstat Networking Displays network information and statistics
newgrp Misc Change to a new group Version 6 AT&T UNIX
nice Process Management Invoke a utility with an altered nice value Version 4 AT&T UNIX
nl Text Processing Line numbering filter
nm C Programming Write the name list of an object file
nohup Process Management Invoke a utility immune to hangups
od Misc Dump files in various formats Version 1 AT&T UNIX
passwd System Set or change user password
paste Text processing Merge corresponding or subsequent lines of files Version 32V AT&T UNIX
patch Text processing Apply changes to files
pathchk Filesystem Check pathnames
pax Misc Portable archive interchange 4.4BSD
pgrep Process Management Find processes with the given name using pattern matching
pkill Process Management Kills processes with the given name using pattern matching
pr Text processing Print files Version 1 AT&T UNIX
printf Shell programming Write formatted output 4.3BSD-Reno
prs SCCS Print an SCCS file
ps Process Management Report process status Version 4 AT&T UNIX
pstree Process Management Display a tree of processes
pwd Filesystem print working directory - Return working directory name
qalter Batch Utilities Alter batch job
qdel Batch Utilities Delete batch jobs
qhold Batch Utilities Hold batch jobs
qmove Batch Utilities Move batch jobs
qmsg Batch Utilities Send message to batch jobs
qrerun Batch Utilities Rerun batch jobs
qrls Batch Utilities Release batch jobs
qselect Batch Utilities Select batch jobs
qsig Batch Utilities Signal batch jobs
qstat Batch Utilities Show status of batch jobs
qsub Batch Utilities Submit a script
read Shell Programming Read a line from standard input
readonly Misc Set the readonly attribute for variables
renice Process Management Set nice values of running processes 4.0BSD
return Shell Programming Return from a function
rm Filesystem Remove files or directories Version 1 AT&T UNIX
rmdel SCCS Remove a delta from an SCCS file
rmdir Filesystem Remove directories Version 1 AT&T UNIX
sact SCCS Print current SCCS file-editing activity
sar System Administration System Activity Report Report System Activity
sccs SCCS Front end for the SCCS subsystem
sed Text processing Stream editor Version 7 AT&T UNIX
seq Misc Print a sequence of numbers
set Misc Set or unset options and positional parameters
sh Shell programming Shell, the standard command language interpreter Version 7 AT&T UNIX
shift Shell programming Shift positional parameters
shopt Shell programing Control optional shell behavior
sleep Shell programming Suspend execution for an interval Version 4 AT&T UNIX
sort Text Processing Sort, merge, or sequence check text files
split Misc Split files into pieces Version 3 AT&T UNIX
strings C Programming Find printable strings in files
strip C Programming Remove unnecessary information from executable files
stty Misc Set the options for a terminal
suspend Shell programming Suspend execution of the shell until it receives a continue signal
tabs Misc Set terminal tabs PWB UNIX
tail Text processing Copy the last part of a file PWB UNIX
talk Misc Talk to another user 4.2BSD
tee Shell programming Duplicate standard input
test Shell programming Evaluate expression
time Process Management Time a simple command Version 3 AT&T UNIX
times Process Management Write process times
touch Filesystem Create file and Change file access and modification times Version 7 AT&T UNIX
top Process Management Real-time display of running processes
tput Misc Change terminal characteristics System V
tr Text processing Translate characters Version 4 AT&T UNIX
trap Process Management Trap signals
true Shell programming Return true value
tsort Text processing Topological sort Version 7 AT&T UNIX
tty Misc Return user's terminal name Version 1 AT&T UNIX
type Misc Displays how a name would be interpreted if used as a command
ulimit Misc Set or report file size limit
umask Misc Get or set the file mode creation mask
umount Filesystem Unmount a filesystem
unalias Misc Remove alias definitions
uname Misc Return system name PWB UNIX
uncompress Misc Expand compressed data 4.3BSD
unexpand Text Processing Convert spaces to tabs 3.0BSD
unget SCCS Undo a previous get of an SCCS file
uniq Text Processing Report or filter out repeated lines in a file Version 3 AT&T UNIX
unlink Filesystem Call the unlink function Version 1 AT&T UNIX
unset Misc Unset values and attributes of variables and functions
uucp Network System-to-system copy
uudecode Network Decode a binary file 4.0BSD
uuencode Network Encode a binary file 4.0BSD
uustat Network uucp status inquiry and job control
uux Process Management Remote command execution
val SCCS Validate SCCS files
vi Text processing Screen-oriented (visual) display editor BSD
wait Process Management Await process completion
wc Text processing Word, line, and byte or character count Version 1 AT&T UNIX
what SCCS Identify SCCS files
who System Administration Display who is on the system Version 1 AT&T UNIX
write Misc Write to another user's terminal Version 1 AT&T UNIX
xargs Shell Programming Construct argument lists and invoke utility PWB UNIX
yacc C Programming Yet another compiler compiler PWB UNIX
zcat Text Processing Expand and concatenate data

Unix-like[edit | edit source]

Like RMS says, "GNU means GNU's Not Unix". Only Unix® is really Unix. Linux and the BSDs are definitely Unix-like though neither one is compliant with the above-mentioned "official" specification. What we present here is based on a set of tools that have been around for a long time. We will be looking at generalizations that behave in similar ways in most *nix environments.

BusyBox[edit | edit source]

BusyBox is a good example of a more basic collection of utilities and are well suited to the novice. They can be found in Mini Linux distributions, such as Tiny Core Linux.

Exercise 1 Go to and check it out.

GNU Core Utilities[edit | edit source]

The GNU Core Utilities are much more extensive and not for the faint at heart. They are found on most full-sized BSD and Linux systems in their full glory.

Command line arguments[edit | edit source]

This section lists arbitrary commands that could be useful. Feel free to add any commands you found useful but are not sure where else to add. Some of these commands may require root access ("sudo").

Devices with example numbers are specified in these examples.

Action Command(s)
List devices of the class "disk" with model number lshw -short -class disk
Details about a specific device (e.g. /dev/sr0) udisksctl info -b /dev/sr0
Spin down hard disk or optical disc drive
  • hdparm -y /deb/sdb
  • sdparm --readonly --command=stop /dev/sr0
Write caching
It improves performance but could lose data if a device is physically disconnected shortly after a file transfer without safe unmounting.

(replace "X" with the correct device name)

  • Deactivate: hdparm -W 0 /dev/sdX
  • Activate: hdparm -W 1 /dev/sdX
  • See status: hdparm -i /dev/sdX
Eject optical disc tray
  • eject /deb/sr0
  • sdparm --readonly --command=eject /dev/sr0
Close optical disc tray
  • eject -t /dev/sr3
  • sdparm --readonly --command=load /dev/sr3
Get size of block device blockdev --getsz /dev/[device]


Other useful commands[edit | edit source]

  • datamash
  • mtail
  • parallel
  • rsync advanced copy and synchronization tool including progress indicator
  • sed stream editor for filtering and transforming text
  • stress (command): stress --cpu 4
  • sudo
  • tr
  • ts adds a timestamp to the beginning of each line of input
  • ls – list files
  • uptime – time since last booting
  • du – disk usage of files and directories
  • df – total disk usage
  • readlink: readlink -f [file path] generates an absolute (full) file path
  • stat – advanced details about a file like multiple date/time stamps, size, inode count, and access rights.
  • losetuploop device utility
  • blockdev – shows information and allows configuring data storage devices, such as read-only mode using blockdev --setro.

External links[edit | edit source]