Basic Unix Commands quick reference

This quick reference lists commands, including a syntax diagram and brief description. […] indicates an optional part of the command.

• For more detail, use: man command

1. Files
1.1. Filename Substitution
Wild Cards                ? *
Character Class (c is any single character) [c…]
Range                 [c-c]
Home Directory         ~
Home Directory of Another User ~user
List Files in Current Directory ls [-l]
List Hidden Files                 ls -[l]a
1.2. File Manipulation
Display File Contents         cat filename
Copy                 cp source destination
Move (Rename)         mv oldname newname
Remove (Delete)         rm filename

1.3. File Properties
Seeing Permissions                ls -l filename
Changing Permissions        chmod nnn filename
                       chmod c=p…[,c=p…] filename

• n, a digit from 0 to 7, sets the access level for the user (owner), group, and others (public), respectively. c is one of: u–user; g–group, o–others, or a–all. p is one of: r–read access, w–write access, or x–execute access.

Setting Default Permissions umask ugo

• ugo is a (3-digit) number. Each digit restricts the default permissions for the user, group, and others, respectively.

Changing Modification Time touch filename
Making Links         ln [-s] oldname newname
Seeing File Types         ls -F

1.4. Displaying a File with less
Run less         less filename
Next line         RETURN
Next Page SPACE
Previous line k
Previous Page b
At end G
Go up U
Quit         q
Search down /
Search up ?

1.5. Directories
Change Directory         cd directory
Make New Directory mkdir directory
Remove Directory         rmdir directory
Print Working (Show Current) Directory pwd

2. Commands
2.1. Command-line Special Characters
Join Words                "…"
Suppress Filename, Variable Substitution '…'
Escape Character                  \
Command Separation          ;
Command-Line Continuation (at end of line) \

2.2. I/O Redirection and Pipes
Standard Output >
(overwrite if exists) >!
Appending to Standard Output >>
Standard Input <
Standard Error and Output >&
Standard Error Separately
( command > output ) >& errorfile
Pipes/Pipelines command | filter [ | filter]

Filters
Word/Line Count wc [-l]
Last n Lines         tail [-n]
Sort lines                 sort [-n]
Multicolumn Output pr -t

2.3. Searching with grep
grep Command grep "pattern" filename
                command | grep "pattern"
Search Patterns
beginning of line         ^
end of line         $
any single character .
single character in list or range […]
character not in list or range [^…]
escapes special meaning \

3. C-Shell Features.
3.1 History Substitution
Repeat Previous Command !!
Commands Beginning with str !str
Commands Containing str !?str[?]
All Arguments to Prev. Command !*
Word Designators
All Arguments :*
Last Argument :$
First Argument :^
n'th Argument         :n
Arguments x Through y :x-y
Modifiers
Print Command Line :p
Substitute Command Line :[g]s/l/r/
3.2 Aliases
alias Command alias name 'definition'

• definition can contain escaped history substitution event and word designators as placeholders for command-line arguments.

3.3. Variable Substitution
Creating a Variable set var
Assigning a Value set var = value
Expressing a Value $var
Displaying a Value echo $var

• value is a single word, an expression in quotes, or an expression that results in a single word after variable, filename and command substitution takes place.

Assigning a List set var = (list)

• list is a space-separated list of words, or an expression that results in a space-separated list.

Selecting the n'th Item $var[n]
Selecting all Items $var
Selecting a Range $var[x-y]
Item Count $#var
3.4 foreach Lists
Start foreach Loop foreach var (list)

• foreach prompts for commands to repeat for each item in list (with >), until you type end. Within the loop, $var stands for the current item in list.

3.5. Command Substitution
Replace Command with its Output on Command Line `…`
3.6 Job Control
Run Command in the Background &
Stop Foreground Job         CTRL-Z
List of Background Jobs          jobs
Bring Job Forward                 %[n]
Resume Job in Background         %[n] &
4. Processes
Listing ps [-[ef]]
Terminating kill [-9] PID

• Timing time command time is a number up to 4 digits. script is the name of a file containing the command line(s) to perform.

5. Users
Seeing Who is Logged In who
                w
Seeing Your User Name whoami

6. Managing Files
6.1. Looking Up Files
Standard Commands whereis file
Aliases and Commands which command
Describe Command whatis command
Searching Out Files find dir -name name -print

• dir is a directory name within which to search. name is a filename to search for.

6.2. Finding Changes
Comparing Files diff leftfile rightfile

• diff prefixes a less-than (<) to selected lines from leftfile and a greater-than (>) to lines from rightfile.

6.3. Automating Tasks
Create a Makefile pico Makefile

• A makefile consists of macro definitions and targets.

Test Makefile make -n [target]
Run make make [target]
6.4. Managing Disk Usage
Check Quota quota -v
Seeing Disk Usage df
        du -s
6.5. Combining and Compressing Files
Create a tarfile tar cf file.tar file1 file2 … fileN

• tar combines files but does not compress 

Create a zipfile zip filename / gzip filename
Unzip a file unzip filename / gunzip filename
7. Printing
7.1 Formatting Output for Printing
Paginate with Page Headers pr filename
in n columns pr -n filename

8. Miscellaneous
8.1 Miscellaneous Commands
List Commands for Subject man -k subject
Display Current Date and Time date
Log off         exit
Display Documentation man command
8.2 Control Keys
Abort Program CTRL-C
Backspace (Delete Last Character) CTRL-H
Pause Display on Screen CTRL-S
Resume Display after CTRL-S CTRL-Q
Send Job to Background CTRL-Z followed by bg