A quick guide to the unix toolset

This page is a "cheat sheet" for Unix/Linux. It quickly explains the more common commands, and shows you how to use them.

General Commands

man man - read the 'man' manual page.
man command - read the 'command' manual page.
man bash - read the 'bash' manual page.
man -k file - list all programs that deal with files.
date - print the current date and time.
cal - print this month's calendar.
cal 2004 - print calendar for 2004.
finger - display information about other users on the system who are logged on.
finger username - look up information about the named user.
who - show who is currently on the system and what they are doing.

ls - list the names of all the files in the current directory.
ls -l - list the names of all the files in the current directory in long format.
ls -a - list all the files, including hidden files, in the current directory.
ls -lrt list the names of all the files in the current directory in long format and reverse chronological order.
ls *.pl - list all the files that have the extension pl.
cat file1 - print the contents of file1 onto the terminal screen.
more file1 - look at file1 one page at a time. Press the space bar to see another page, the return key to see another line. Type q to quit.
head file1 - print the first 10 lines of file1.
tail file1 - print the last 10 lines of file1.
head -30 file1 - print the first 30 lines of file1.
cp file1 file2 - make a copy of file1 and call it file2.
mv file1 file2 - change the name of file1 to be file2.
gzip large-file - compresses large-file using gzip. gunzip large_file restores original file condition.

grep word file1 - look through file1 for case sensitive match on word and print the line that contains word.
grep -i word file1 - look through file1 for case insensitive match on word and print the line that contains word.
grep -v word file1- look through file1 for case sensitive match on word and print the line that do not contain word.
grep -l word * - look through all the files in the current directory and print the names of those files which contain word.
wc file1 - count lines, words, and characters in file1.
wc -l file1 - count lines in file1.
wc -l /usr/dict/words - count the number of lines (words ) in /usr/dict/words
spell file1 - list spelling errors in file1
sort file1 - sorts the contents of file1. See man sort for details.

pwd - print the current working directory
cd dir1 - change directory to dir1. cd with no argument changes back to the user's home directory.
mkdir myfiles - create a new directory named myfiles.
rmdir myfiles - deletes a directory named myfiles (must be empty).
rm file1 - deletes file1
touch file1 - creates and empty file called file1
chmod - change protection of files. chmod o-r file1 makes file1 unreadable to people outside of the owner's group. See man chmod for more details.
chown - change ownership of files. See man chown for more details.
find . -name file1.pl -print - searches down through all your directories to find files named file1.pl Prints their path names when it finds them. See man find for more details.
quota -v - displays the quota you have available. Note: you will only have quota on your own partition.
du -k - list your disk usage in kilobytes.

jobs - show any background jobs.
fg %1 - bring job 1 to the foreground.
kill %1 - kill background job number 1.
passwd - change your password.
ps - list all your running processes.
ps -ef - list all running processes on the system.
kill 12345 - kills process 12345. Note: you can only kill processes you own.
groups - list the unix group you are a member of.
groups username - list the unix groups username is a member of.
telnet hostname - connects you to a remote system called hostname.
ssh hostname - connects you to a remote system called hostname using secure shell.

tail -20 file1 > file2 - take the last 20 lines from file1 and dump them into file 2. Contents of file2 will be overritten.
tail -20 file1 >> file2 - take the last 20 lines from file1 and append them to file 2.
ps -ef | grep bash - list all the users running bash proceses.
ps -ef | grep bash| sort - list all the users running bash proceses and sort on the first column (username).
ps -ef | grep root | wc -l - count the number of processes being run by root.
grep cie /usr/share/dict/words | wc -l - how many words in /usr/share/dict/words have i before e after c?