Simple Unix Commands

COMMAND	DESCRIPTION	USAGE EXAMPLE	NOTES ON EXAMPLE
man	view the online documentation	man cd	The manual pages for the cd command are displayed at your terminal.
cat / more / less	list a file on standard output (default standard output is the terminal)	cat .bashrc	The contents of the .bashrc file are displayed. cat displays the whole file at once, whereas more and less display a screen at a time.
head	list the beginning of a file on standard output	head -50 myfile	The first 50 lines of “myfile” are displayed.
tail	list the end of a file on standard output	tail -70 myfile	The last 70 lines of “myfile” are displayed.
cp	copy a file	cp oldfile newfile	A copy of “oldfile” is made, and saved as “newfile”.
mv	move a file	mv oldfile newfile	The file “oldfile” is moved (renamed) to a file called “newfile”.
rm	remove / delete a file	rm tempfile	Remove (delete) the file called temp.
ls	list the contents of a directory	ls mydir	Lists the contents for the “mydir” directory. If the directory name is omitted, current directory is assumed.
chmod	change the access permissions of a file	chmod ugo+rwx file	Allow owner, group and others read, write and execute permission for file.
pwd	print working directory	pwd	Gives the full pathname of the directory in which you are currently working.
cd	change directory	cd subdir	Change to a “subdir” directory as specified.
mkdir	make / create a new directory	mkdir subdir	Creates a directory called subdir as a subdirectory of your current directory.
rmdir	remove / delete a directory	rmdir subdir	Removes subdir, only if it is empty (contains no files).
vi	invoke the vi (vim) editor	vi newfile	Edit the file newfile. If newfile does not exist, an empty file is opened for editing.
diff	compare two files and show the differences	diff file1 file2	Compares file1 with file2.
grep	search for a regular expression in a file	grep error file1	Prints out every line of the file “file1” which contains the string “error”. Additionally, you can also use wildcards in the search pattern.
kill	terminate a process which is owned by you	kill 1234	Terminate the process with process id 1234 .