Unix Cheat Sheet

Lifted from http://www.rain.org/~mkummel/unix.html and slightly modified

Help on any Unix command.

man {command}

Type man ls to read the manual for the ls command.

man {command} > {filename}

Redirect help to a file to download.

man –k (key word)

List all commands with (key word) in the description

whatis {command}

Give short description of command.

apropos {keyword}

Search for all Unix commands that match keyword, eg apropos file.

List a directory

ls {path}

It's ok to combine attributes, eg ls -laF gets a long listing of all files with types.

ls {path_1} {path_2}

List both {path_1} and {path_2}.

ls -l {path}

Long listing, with date, size and permisions.

ls -a {path}

Show all files, including important .dot files that don't otherwise show.

ls -F {path}

Show type of each file. "/" = directory, "*" = executable.

ls -R {path}

Recursive listing, with all subdirs.

ls {path} > {filename}

Redirect directory to a file.

ls {path} | more

Show listing one screen at a time.

dir {path}

Useful alias for DOS people

Change to directory

cd {dirname}

There must be a space between.

cd ~

Go back to home directory, useful if you're lost.

cd ..

Go back one directory.

cdup

Useful alias, like "cd ..",

Make a new directory

mkdir {dirname}

Remove a directory

rmdir {dirname}

Only works if {dirname} is empty.

rm -r {dirname}

Remove all files and subdirs. Careful!

Print working directory

pwd

Show where you are as full path. Useful if you're lost or exploring.

Copy a file or directory

cp {file1} {file2}

cp -r {dir1} {dir2}

Recursive, copy directory and all subdirs.

cat {newfile} >> {oldfile}

Append newfile to end of oldfile.

Move (or rename) a file

mv {oldfile} {newfile}

Moving a file and renaming it are the same thing.

mv {oldname} {newname}

Delete a file

rm {filespec}

? and * wildcards work like DOS should. "?" is any character; "*" is any string of characters.

ls {filespec}
rm {filespec}

Good strategy: first list a group to make sure it's what's you think...
...then delete it all at once.

View a text file

more {filename}

View file one screen at a time.

less {filename}

Like more, with extra features.

cat {filename}

View file, but it scrolls.

cat {filename} | more

View file one screen at a time.

Edit a text file.

xemacs {filename}

Create a text file.

cat > {filename}

Enter your text (multiple lines with enter are ok) and press control-d to save.

xemacs {filename}

Create some text and save it.

Compare two files

diff {file1} {file2}

Show the differences.

sdiff {file1} {file2}

Show files side by side.

Other text commands

grep '{pattern}' {file}

Find regular expression in file.

sort {file1} > {file2}

Sort file1 and save as file2.

sort -o {file} {file}

Replace file with sorted version.

spell {file}

Display misspelled words.

wc {file}

Count words in file.

time {file}

Run program file and output real time to run (duration of execution), user time, and system time.

Find files on system

find {filespec}

Works with wildcards. Handy for snooping.

find {filespec} > {filename}

Redirect find list to file. Can be big!

Make an Alias

alias {name} '{command}'

Put the command in 'single quotes'. More useful in your .cshrc file.

Wildcards and Shortcuts

*

Match any string of characters, eg page* gets page1, page10, and page.txt.

?

Match any single character, eg page? gets page1 and page2, but not page10.

[...]

Match any characters in a range, eg page[1-3] gets page1, page2, and page3.

~

Short for your home directory, eg cd ~ will take you home, and rm -r ~ will destroy it.

.

The current directory.

..

One directory up the tree, eg ls ...

Pipes and Redirection

(You pipe a command to another command, and redirect it to a file.)

{command} > {file}

Redirect output to a file, eg ls > list.txt writes directory to file.

{command} >> {file}

Append output to an existing file, eg cat update >> archive adds update to end of archive.

{command} < {file}

Get input from a file, eg sort < file.txt

{command} < {file1} > {file2}

Get input from file1, and write to file2, eg sort < old.txt > new.txt sorts old.txt and saves as new.txt.

{command} | {command}

Pipe one command to another, eg ls | more gets directory and sends it to more to show it one page at a time.

Permissions, important and tricky!

Unix permissions concern who can read a file or directory, write to it, and execute it. Permissions are granted or withheld with a magic 3-digit number. The three digits correspond to the owner (you); the group (?); and the world (everyone else).

Think of each digit as a sum:

execute permission	= 1
write permission	= 2
write and execute (1+2)	= 3
read permission	= 4
read and execute (4+1)	= 5
read and write (4+2)	= 6
read, write and execute (4+2+1)	= 7

Add the number value of the permissions you want to grant each group to make a three digit number, one digit each for the owner, the group, and the world. Here are some useful combinations. Try to figure them out!

chmod 600 {filespec}

You can read and write; the world can't. Good for files.

chmod 700 {filespec}

You can read, write, and execute; the world can't. Good for scripts.

chmod 644 {filespec}

You can read and write; the world can only read. Good for web pages.

chmod 755 {filespec}

You can read, write, and execute; the world can read and execute. Good for programs you want to share, and your public_html directory.

Permissions, another way

You can also change file permissions with letters:

u = user (yourself)	g = group	a = everyone
r = read	w = write	x = execute

chmod u+rw {filespec}

Give yourself read and write permission

chmod u+x {filespec}

Give yourself execute permission.

chmod a+rw {filespec}

Give read and write permission to everyone.

System info

date

Show date and time.

df

Check system disk capacity.

du

Check your disk usage and show bytes in each directory.

more /etc/motd

Read message of the day, "motd" is a useful alias..

printenv

Show all environmental variables (in C-shell% - use set in Korn shell$).

quota -v

Check your total disk use.

uptime

Find out system load.

w

Who's online and what are they doing?

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Unix Directory Format

Long listings (ls -l) have this format:

 
 - file
 d directory, * executable
 ^ symbolic links (?) file size (bytes) file name / directory
 ^ ^ ^ ^ ^
 drwxr-xr-x 11 mkummel 2560 Mar 7 23:25 public_html/
 -rw-r--r-- 1 mkummel 10297 Mar 8 23:42 index.html
 ^
 ^^^ user permission (rwx) last mod time
 ^^^ group permission (rwx)
 ^^^ world permission (rwx)

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Dotfiles (aka Hidden Files)

Dotfile names begin with a "." These files and directories don't show up when you list a directory unless you use the -a option, so they are also called hidden files. Type ls -la in your home directory to see what you have.

Some of these dotfiles are crucial. They initialize your shell and the programs you use, like autoexec.bat in DOS and .ini files in Windows. rc means "run commands". These are all text files that can be edited, but change them at your peril. Make backups first!

Here's some of what I get when I type ls -laF:

.addressbook	my email addressbook.
.cshrc	my C-shell startup info, important!
.gopherrc	my gopher setup.
.history	list of past commands.
.login	login init, important!
.lynxrc	my lynx setup for WWW.
.ncftp/	hidden dir of ncftp stuff.
.newsrc	my list of subscribed newsgroups.
.pinerc	my pine setup for email.
.plan	text appears when I'm fingered, ok to edit.
.profile	Korn shell startup info, important!
.project	text appears when I'm fingered, ok to edit.
.signature	my signature file for mail and news, ok to edit.
.tin/	hidden dir of my tin stuff for usenet.
.ytalkrc	my ytalk setup.

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DOS and UNIX commands

Action	DOS	UNIX
change directory	cd	cd
change file protection	attrib	chmod
compare files	comp	diff
copy file	copy	cp
delete file	del	rm
delete directory	rd	rmdir
directory list	dir	ls
edit a file	edit	pico
environment	set	printenv
find string in file	find	grep
help	help	man
make directory	md	mkdir
move file	move	mv
rename file	ren	mv
show date and time	date, time	date
show disk space	chkdsk	df
show file	type	cat
show file by screens	type filename | more	more
sort data	sort	sort

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