List of POSIX commands

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Utilities listed in POSIX.1-2017

This is a list of the shell commands of the most recent version of the Portable Operating System Interface (POSIX) – IEEE Std 1003.1-2024 which is part of the Single UNIX Specification (SUS). These commands are implemented in many shells on modern Unix, Unix-like and other operating systems. This list does not cover commands for all versions of Unix and Unix-like shells nor other versions of POSIX.

As is typical in the context of a POSIX system, the term file refers to an item of a file system which can be a regular file, a directory or several other more specialized types.

Columns:

Command The text one enters to launch the command. Category Functional categorization. Optionality Indicates whether the command is mandatory or optional in order to achieve conformance. If the latter, then a code indicates the optional functionality group to which the command belongs. Batch environment (BE) Batch job control. C‑language development (CD) For developing software in C. FORTRAN development (FD) For developing software in FORTRAN. FORTRAN runtime (FR) Runtime‑support for FORTRAN. Software development (SD) For developing software; not language specific. User portability (UP) Addresses consistency at the user interface level. X/Open System Interfaces (XSI) Historically UNIX-like features that were common on System V–style systems. Description Describes what the command does. First appeared Identifies an operating system version in which the command was first provided.
Command Category Optionality Description First appeared
admin SCCS Optional (XSI) Create and administer SCCS files PWB UNIX
alias Misc Mandatory Manage command aliases
ar Misc Mandatory Manage library archives Version 1 AT&T UNIX
asa Text processing Optional (FR) Interpret carriage-control characters System V
at Process management Mandatory Execute commands at a later time Version 7 AT&T UNIX
awk Text processing Mandatory Pattern scanning and processing language Version 7 AT&T UNIX
basename Filesystem Mandatory Report non-directory portion of a pathname Version 7 AT&T UNIX
batch Process management Mandatory Schedule commands to be executed in a batch queue
bc Misc Mandatory Arbitrary-precision arithmetic calculator Version 6 AT&T UNIX
bg Process management Optional (UP) Move jobs to the background
cc C programming Optional (CD) Compile C source code IEEE Std 1003.1-2024
cal Misc Optional (XSI) Print a calendar Version 5 AT&T UNIX
cat Filesystem Mandatory Concatenate and print files PDP-7 UNIX
cd Filesystem Mandatory Change the working directory Version 6 AT&T UNIX
cflow C programming Optional (XSI) Generate a C-language call graph System V
chgrp Filesystem Mandatory Change file group ownership PWB UNIX
chmod Filesystem Mandatory Change file modes/attributes/permissions PDP-7 UNIX
chown Filesystem Mandatory Change file ownership PDP-7 UNIX
cksum Filesystem Mandatory Report file checksum and size 4.4BSD
cmp Filesystem Mandatory Compare two files Version 1 AT&T UNIX
comm Text processing Mandatory Select or reject lines common to two files Version 4 AT&T UNIX
command Shell programming Mandatory Execute a simple command
compress Filesystem Optional (XSI) Compress data 4.3BSD
cp Filesystem Mandatory Copy files PDP-7 UNIX
cron Misc Mandatory Schedule periodic background work System V
csplit Text processing Mandatory Split files based on context PWB UNIX
ctags C programming Optional (SD) Create a tags file 3BSD
cut Text processing Mandatory Cut out selected fields of each line of a file System III
cxref C programming Optional (XSI) Generate a C-language program cross-reference table System V
date Misc Mandatory Report or change system date and time Version 1 AT&T UNIX
dd Filesystem Mandatory Convert and copy files Version 5 AT&T UNIX
delta SCCS Optional (XSI) Make a delta (change) to an SCCS file PWB UNIX
df Filesystem Mandatory Report free storage space Version 1 AT&T UNIX
diff Text processing Mandatory Compare two files Version 5 AT&T UNIX
dirname Filesystem Mandatory Report the directory portion of a pathname System III
du Filesystem Mandatory Estimate file space usage Version 1 AT&T UNIX
echo Shell programming Mandatory Write to standard output Version 2 AT&T UNIX
ed Text processing Mandatory The standard text editor PDP-7 UNIX
env Misc Mandatory Set the environment for command invocation System III
ex Text processing Optional (UP) Text editor 1BSD
expand Text processing Mandatory Convert tabs to spaces 3BSD
expr Shell programming Mandatory Evaluate arguments as an expression Version 7 AT&T UNIX
false Shell programming Mandatory Exit immediately with status 1 Version 7 AT&T UNIX
fc Misc Optional (UP) Process the command history list
fg Process management Optional (UP) Move a job to the foreground
file Filesystem Mandatory Report type of files Version 4 AT&T UNIX
find Filesystem Mandatory Find files Version 1 AT&T UNIX
fold Text processing Mandatory Filter for folding lines 1BSD
fuser Process management Optional (XSI) List process IDs of all processes that have one or more files open System V
gencat Misc Mandatory Generate a formatted message catalog
get SCCS Optional (XSI) Get a version of an SCCS file PWB UNIX
getconf Misc Mandatory Get configuration values
getopts Shell programming Mandatory Parse utility options
gettext Misc Mandatory Retrieve text string from messages object
grep Misc Mandatory Search text for a pattern Version 4 AT&T UNIX
hash Misc Mandatory Hash database access method
head Text processing Mandatory Copy the first part of files PWB UNIX[citation needed]
iconv Text processing Mandatory Codeset conversion HP-UX
id Misc Mandatory Report user identity System V
ipcrm Misc Optional (XSI) Remove a message queue, semaphore set, or shared memory segment identifier System V
ipcs Misc Optional (XSI) Report interprocess communication facilities status System V
jobs Process management Optional (UP) Report background jobs
join Text processing Mandatory Merges two sorted text files based on the presence of a common field Version 7 AT&T UNIX
kill Process management Mandatory Terminate or signal processes Version 4 AT&T UNIX
lex C programming Optional (CD) Generate programs for lexical tasks Version 7 AT&T UNIX
link Filesystem Optional (XSI) Create a hard link to a file Version 1 AT&T UNIX
ln Filesystem Mandatory Link files Version 1 AT&T UNIX
locale Misc Mandatory Get locale-specific information
localedef Misc Mandatory Define locale environment
logger Shell programming Mandatory Log messages 4.3BSD
logname Misc Mandatory Report the user's login name 4.4BSD
lp Text processing Mandatory Send files to a printer System V
ls Filesystem Mandatory List directory contents Version 1 AT&T UNIX
m4 Misc Mandatory Macro processor PWB UNIX
mailx Misc Mandatory Process messages Version 1 AT&T UNIX
make Programming Optional (SD) Maintain, update, and regenerate groups of programs PWB UNIX
man Misc Mandatory Display system documentation Version 2 AT&T UNIX
mesg Misc Mandatory Permit or deny messages Version 1 AT&T UNIX
mkdir Filesystem Mandatory Make directories Version 1 AT&T UNIX
mkfifo Filesystem Mandatory Make FIFO special files 4.4BSD[dubious – discuss]
more Text processing Optional (UP) Display files on a page-by-page basis 3BSD
msgfmt Misc Mandatory Create messages objects from messages object files
mv Filesystem Mandatory Move or rename files Version 1 AT&T UNIX
newgrp Misc Mandatory Change to a new group Version 6 AT&T UNIX
ngettext Misc Mandatory Retrieve text string from messages object with plural form
nice Process management Mandatory Invoke a utility with an altered nice value Version 4 AT&T UNIX
nl Text processing Optional (XSI) Line numbering filter System III
nm C programming Optional
(SD, XSI) 		Write the name list of an object file Version 1 AT&T UNIX
nohup Process management Mandatory Invoke a utility immune to hangups Version 4 AT&T UNIX
od Misc Mandatory Dump files in various formats Version 1 AT&T UNIX
paste Text processing Mandatory Merge corresponding or subsequent lines of files Version 32V AT&T UNIX
patch Text processing Mandatory Apply changes to files 4.3BSD
pathchk Filesystem Mandatory Check pathnames
pax Misc Mandatory Portable archive interchange 4.4BSD[citation needed]
pr Text processing Mandatory Paginate or columnate files for printing Version 1 AT&T UNIX
printf Shell programming Mandatory Write formatted output 4.3BSD-Reno
prs SCCS Optional (XSI) Print an SCCS file PWB UNIX
ps Process management Mandatory Report process status Version 4 AT&T UNIX
pwd Filesystem Mandatory Print working directory Version 5 AT&T UNIX
read Shell programming Mandatory Read a line from standard input
readlink Filesystem Mandatory Print destination of a symbolic link
realpath Filesystem Mandatory Report the fully qualified path of a file XPG4[1]
renice Process management Mandatory Set nice values of running processes 4BSD
rm Filesystem Mandatory Remove file(s) Version 1 AT&T UNIX
rmdel SCCS Optional (XSI) Remove a delta from an SCCS file PWB UNIX
rmdir Filesystem Mandatory Remove empty directory(ies) Version 1 AT&T UNIX
sact SCCS Optional (XSI) Print current SCCS file-editing activity System III
sccs SCCS Optional (XSI) Front end for the SCCS subsystem 4.3BSD
sed Text processing Mandatory Stream editor Version 7 AT&T UNIX
sh Shell programming Mandatory Shell, the standard command language interpreter Version 7 AT&T UNIX
(in earlier versions, sh was either the Thompson shell or the PWB shell)
sleep Shell programming Mandatory Suspend execution for an interval Version 4 AT&T UNIX
sort Text processing Mandatory Sort, merge, or sequence check text files Version 1 AT&T UNIX
split Misc Mandatory Split files into pieces Version 3 AT&T UNIX
strings C programming Mandatory Find printable strings in files 2BSD
strip C programming Optional (SD) Remove unnecessary information from executable files Version 1 AT&T UNIX
stty Misc Mandatory Set the options for a terminal Version 2 AT&T UNIX
tabs Misc Mandatory Set terminal tabs PWB UNIX
tail Text processing Mandatory Copy the last part of a file PWB UNIX[citation needed]
talk Misc Optional (UP) Talk to another user 4.2BSD
tee Shell programming Mandatory Duplicate the standard output Version 5 AT&T UNIX
test Shell programming Mandatory Evaluate expression Version 7 AT&T UNIX
time Process management Mandatory Display elapsed, system and kernel time used by the current shell or designated process. Version 3 AT&T UNIX[2]
timeout Process management Mandatory Run command with a time limit Version 3 AT&T UNIX
touch Filesystem Mandatory Change file access and modification times Version 7 AT&T UNIX
tput Misc Mandatory Change terminal characteristics System V
tr Text processing Mandatory Translate characters Version 4 AT&T UNIX
true Shell programming Mandatory Exit immediately with status 0 Version 7 AT&T UNIX
tsort Text processing Mandatory Topological sort Version 7 AT&T UNIX
tty Misc Mandatory Report user's terminal name Version 1 AT&T UNIX
type Misc Optional (XSI) Displays how a name would be interpreted if used as a command
ulimit Misc Optional (XSI) Set or report file size limit
umask Misc Mandatory Get or set file mode creation mask System III
unalias Misc Mandatory Remove alias definitions
uname Misc Mandatory Report system name PWB UNIX
uncompress Misc Optional (XSI) Expand compressed data 4.3BSD
unexpand Text processing Mandatory Convert spaces to tabs 3BSD
unget SCCS Optional (XSI) Undo a previous get of an SCCS file System III
uniq Text processing Mandatory Report or filter out repeated lines in a file Version 3 AT&T UNIX
unlink Filesystem Optional (XSI) Call the unlink function Version 1 AT&T UNIX
uucp Network Optional (UU) System-to-system copy Version 7 AT&T UNIX
uudecode Network Mandatory Decode a binary file 4BSD
uuencode Network Mandatory Encode a binary file 4BSD
uustat Network Optional (UU) uucp status inquiry and job control System III
uux Process management Optional (UU) Remote command execution Version 7 AT&T UNIX
val SCCS Optional (XSI) Validate SCCS files System III
vi Text processing Optional (UP) Screen-oriented (visual) display editor 1BSD
wait Process management Mandatory Await process completion Version 4 AT&T UNIX
wc Text processing Mandatory Line, word and byte or character count Version 1 AT&T UNIX
what SCCS Optional (XSI) Identify SCCS files PWB UNIX
who System administration Optional (XSI) Display who is on the system Version 1 AT&T UNIX
write Misc Mandatory Write to another user's terminal Version 1 AT&T UNIX
xargs Shell programming Mandatory Construct argument lists and invoke utility PWB UNIX
xgettext C programming Optional (CD) Extract gettext calls from C source code strings IEEE Std 1003.1-2024
yacc C programming Optional (CD) Yet another compiler compiler PWB UNIX
zcat Text processing Optional (XSI) Expand and concatenate compressed data 4.3BSD

See also

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References

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  1. ^ IEEE Computer Society (December 1, 2008). "POSIX.1-2008 System Interfaces: realpath()". The Open Group. Base Specifications (Issue 7). doi:10.1109/IEEESTD.2008.4694976. ISBN 978-0-7381-4048-3. Archived from the original on September 18, 2024. Retrieved October 27, 2025. First released in CAE Specification: System Interface Definitions (XBD), Issue 4, Version 2 (August 1994).
  2. ^ "FreeBSD Manual Pages: time". man.freebsd.org. July 7, 2020. Retrieved Mar 23, 2025.
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