Important & Useful Unix Commands

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
Create or Modify file: pico 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

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

Quotes and Escape Join Words “…”
Suppress Filename, Variable Substitution ‘…’
Escape Character : \
Separation, Continuation : 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 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
List Spelling Errors ispell

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 : [^…]
zero or more of preceding char. or pattern : *
zero or more of any character : .*
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  -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 – who am i

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 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
Unzip a file unzip filename

7. Printing
7.1 Formatting Output for Printing
Paginate with Page Headers pr filename
in n columns pr -n filename
Format for Laser Printer tex document

7.2 The Printer Queue
Print a File : lp [-dpr] filename
Check Quota : lpquot
List Queue : lpq
Stop Job : lprm

8. Miscellaneous
8.1 Miscellaneous Commands
List Commands for Subject : man -k subject
Display Current Date and Time : date
Log off : exit
Electronic Mail : pine
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