Unix Cheat Sheet

List a directory		Alternatively, type 'ls --help' or 'man ls' for more information
	ls [path]	list given path without any options. Without the path, it is listing current directory
	ls -l [path]	list given path in long listing format
	ls -h [path]	list given path in human readable format
	ls -a [path]	list given path, including hidden files (which has prefix dot)
	ls -lrt [path]	list given path, combining different options. long listing format, sort by modification time in reverse order
	ls [path]	list given path, redirect listing results into a file
	ls [path] | more	list given path, showing listing results on one screen at a time
Change to a directory
	cd <directory>	change to the given directory
	cd ~	change to user's home directory
	cd /	change to root directory
	cd ..	go to parent directory
	cd ../<directory>	go to a sibling directory
Print current working directory
	pwd	display the current working directory
Create directory(ies)
	mkdir <directory>	create the directory under current working directory
	mkdir -p <dir1>/<dir2>	create directory2 under directory1; create parent directory2 as needed
Remove files or directory(ies)
	rm <file>	remove the file
	rm -rf <directory>	remove the contents of given directory recursively without prompt
Move a file or a directory
	mv <source> <dest>	rename source as dest, and move source to dest
Copy a file or a directory
	cp <source> <dest>	make a copy from source to dest
	cp -r <source> <dest>	copy recursively from source directory to dest directory
Download a file from http website
	wget <url>	download the resource to current directory
	curl <url>	download the resource to current directory
View a text file
	less <file>	view file page by page, with a lot of features
	more <file>	view file with screen length
	cat <file>	view file, but it will scroll to the end of file
	cat <file> | more	view file, and piped the file content to more command
Create a text file
	touch <file>	create an empty file
	vi <file>	use vi text editor to create a file (need to save the file though)
	echo "foo" >> <file>	create a file with content 'foo'
	cat > <file>	enter multi-line texts and press control-d to save the content to a file
Change a file's modification or access time
	stat <file1>	display the stat of given file
	touch -m -d '1 Mar 2013 02:53' file.txt	change the modification time of file.txt to be '1 Mar 2013 02:53', and create the file if it doesn't exist
	touch -a -d '1 Mar 2013 02:53' file.txt	change the access time of file.txt to be '1 Mar 2013 02:53', and create the file if it doesn't exist
Compare two files
	diff <file1> <file2>	show the differences between file1 and file2
	sdiff <file1> <file2>	show file1 and file2 side by side
Pipes and redirections
	<command> > <file>	redirect command output to a file, e.g. ll > file.txt writes current directory listings to file.txt
	<command> >> <file>	appends command output to the end of a file
	<command> < <file>	redirect the standard input from the file
	<command> < <file1> > <file2>	redirect the standard input from the file1, and then redirect the standard output to file2
	<command1> | <command2>	pipe the output of command1 as the input of command2
File permissions		read=4, write=2, execute=1
	chmod 700 <file(s)>	file(s) owner can read, write and execute
	chmod 600 <file(s)>	file(s) owner can read and write, but not execute
	chmod 400 <file(s)>	file(s) owner can read only
	chmod 755 <file(s)>	file(s) owner can read, write and execute; both group owner and others can read and write
	chmod 644 <file(s)>	file(s) owner can read and write; both group owner and others can read only
	chmod u+x <file(s)>	grant file(s) owner execute permission
	chmod u-x <file(s)>	remove execute permission from file(s) owner
	chmod a+rw <file(s)>	grant everyone read and write permission to the file(s)
Other useful comands
	df -h	report file system disk space usage in human readable format
	du -h	estimate file space usage in human readable format
	date	display or set the current system date and time
	top	display linux tasks, as well as CPU and memory stats
	ps -aef	display a snapshot of current processes
	ln -s <target> <link_name>	create a symbolic link to the target with link_name
	alias	display current defined aliases or create an alias
	!<command>	invoke previous run of the given command