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Quick Summary of Important Unix Commands

In the table on the next page a variety of the most important Unix commands are listed with their common usage and a brief description. This is intended only as a quick reference; check the man pages for more details. Entries in italics are built-in shell commands (csh) and entries underlined are used most frequently in scripts. Square brackets [ ] indicate optional arguments. An ellipsis ... indicates multiple arguments of the given type are supported. Note that the syntax for arguments varies between commands (e.g. whether you can use -al in place of -a -l); unfortunately only the man page can tell you for sure.

Command with Common Usage Description
alias [ name [ string ] ] Make name an alias for string
awk script [ file ] See description below
basename [ path ] Return everything after last / in path
bg [ %job-id ] Put job in the background
break Escape from control loop
cat [ file ... ] Concatenate and display files
cd [ dir ] Change working directory
chmod mode file Change permissions mode of file
continue Continue next iteration of control loop
cp source target Copy source file to target file
diff file1 file2 Display differences between file1 and file2
dirname [ path ] Return everything before last / in path
echo [ -n ] string Write string to standard output
exit [ value ] Exit from current shell with optional return value
fg [ %job-id ] Return job to foreground
foreach word ( list ) [ ... ] end Succesively set word to elements in list
grep [ -i ] pattern [ file ] Search for pattern in file
head [ -number ] [ file ] Print first few lines of file
hostname Print name of current host
if ( expr ) [ then ... else ... endif ] Conditional evaluation (else if also supported)
kill [ -signal ] pid Terminate or signal a process
ln -s source [ target ] Make symbolic link from target to source
ls [ -alrt ] List contents of directory
make Maintain and regenerate related programs and files
man [ -k ] command Display man page for a command or keyword
mkdir dir Make directory
more [ file ... ] Browse or page through a text file
mv source target Move or rename source to target
nice [ -priority ] command Execute command with specific priority
ps Print information about active processes
pwd Return working directory name
rehash Refresh command search path
renice priority pid Change process priority
rm file Remove file
rmdir dir Remove directory
sed script [ file ] See description below
set [ variable [ = value ] ] Set shell variable to value (opposite unset)
setenv [ VARIABLE [ word ] ] Set environment variable to word (opposite unsetenv)
sort [ file ] Sort lines of text file
source file Execute commands from text file
switch ( expr ) case: [ ... ] endsw Choose from among a list of actions (like in C)
tail [ -number ] [ file ] Print last few lines of file
tee [ file ] Replicate standard output
time command Time a command
top Display information about top CPU processes
touch file Create empty file or update access & mod times
uptime Show system load and how long system has been up
w Display information about logged-in users
wc [ file ... ] Count lines, characters, and bytes in file
whatis command Display summary about a command
which command (also where command) Locate a command; display its pathname or alias
while ( expr ) [ ... ] end Loop while expr true

next up previous
Next: Using I/O Streams Up: intro_Unix Previous: System Information
Massimo Ricotti 2009-01-26