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UNIX Shell in 10 mins

Unix File System

Directory Structure and notations.

~                       -> HOME directory 
.                       -> current directory 
..                      -> parent directory 
../../                  -> parent of parent and can be used in any combination
*.jpg                   -> [Wildcard notation] select all files with extension `jpg` in current directory 
~/Documents/*.doc       -> [Wildcard notation] select all files with extension `doc` in [HOME_DIRECTORY]/Documents/

Also take a look at this badunixhabits guide.

Basic Unix Shell Commands

Summary

command Function Example Syntax -OPTIONS
pwd pathname for the current directory pwd
ls List files ls -l [DIR/PATH/WILDCARDS] -ltrha
file displays file type file [DIR/PATH/WILDCARDS]
cd Change Directory cd [DIRNAME/PATH]
mkdir Make Directory mkdir [DIRNAME/PATH] -p (path)
touch Create a new empty File touch [FILENAME]
cat Display contents of a File cat [FILENAME] -n (line#)
mv move/ rename mv [SOURCE][DESTINATION]
cp copy cp [SOURCE][DESTINATION] -rf
rm remove/ delete rm [DIRNAME/FILENAME] -rf
locate locate a file with name locate [FILENAME] -inc
man displays usage manual man [UNIX COMMAND]
history displays history of commands history !-3

For more -OPTIONS try man [COMMAND]

ls - List files

The ls command is used to list the contents of a directory. It is probably the most commonly used Linux command. It can be used in a number of different ways. Here are some examples: 

ls -options arguments

ls                  # List the files in the working directory

ls /bin             # List the files in the /bin directory (or any other directory you care to specify)

ls -l               # List the files in the working directory in long format

ls -l /etc /bin     #  List the files in the /bin directory and the /etc directory in long format

ls -la ..           # List all files (even ones with names beginning with a period character, which are normally hidden) in the parent of the working directory in long format

Wild Cards * and ?

ls *.doc            # List all files ending with '.doc' 
ls hello*           # List all files starting with 'hello'
ls ??ll*            # List all files with 3,4th chars 'll'

cd - Change Directory

Change Directory to the path specified, for example cd projects. There are a few really helpful arguments to aid this:

cd [DIRECTORY_NAME or PATH]     # navigate to  DIR or PATH
cd ~                            # ~ is HOME directory of user also same as
cd $HOME
cd ../..                        # navigate up 2 levels

mkdir - Make Directory

Make directories with this command mkdir my_folder . Not only can it make the folder specified, but also its parents if they do not exist already using the -p option. The command 

mkdir [DIRECTORY_NAME]

mkdir -p first_folder/next_folder/my_folder 
# To create multiple new nested folder: 
# the first, next folder and the next on path

There is an option to set the mode, or permissions, via the -m flag, and these can be changed later with the chmod command (see below for more on mode and permissions).

touch - Create a File

Create an empty file. Touches the file to update the access and or modification date of a file or directory without opening, saving or closing the file. But one of the most common uses is to create an empty file touch my_file.

touch [FILENAME]            # creates a blank file called 'FILENAME'

cat - Display content of a File

Concatenate and print files to stdout cat my_file. This command is only for view/ preview. You can pass one or more file names to this command, and even number the lines using the -n to number the lines. Close cousin of this is more, head, tail. Also you can use vi to launch a terminal-based text editor. 

cat [FILENAME]              # to show whole file in stdout (terminal)
cat [FILENAME] -n           # print line numbers in stdout (terminal)
cat [FILENAME_1] [FILENAME_2] [..]

mv - move or rename

Moves files and folders. The first argument is the file you want to move, and the second is the location to move it to. Use the flags -f to force move them and -i to prompt confirmation before overwriting files.

Moving Files and Directories 

mv [SOURCE_FILE OR DIRECTORY] [DESTINATION_FILE OR DIRECTORY]

cp - copy

Copies files and folders cp my_file ./projects . The flag -r recursively copies subfolders and files.

Copying Files

cp [SOURCE_FILE] [DESTINATION_FILE]

Copying Directories ( -r option )

cp -r [SOURCE DIRECTORY] [DESTINATION DIRECTORY]    # -r options needed to move files recursively

rm - remove/ delete

Removes files and folders rm my_folder. Options below

rm [FILENAME or WILDCARDS]

# removes all file in the current folder with extension jpg and txt
rm *.jpg *.txt

# Using -r will again recursively delete subfolders, -f force deletes, and -rf for a recursive force delete. 
rm -r [DIRECTORY_NAME]


# If you want to remove all folders and files in the current directory the command is 
rm -rf ./*

man - manual

Manuals for a command can be shown with this instruction. Below is some of the output from running man ls, it also displays all the options available for running the command.

man ls

LS(1)                     BSD General Commands Manual                    LS(1)
NAME
    ls -- list directory contents
SYNOPSIS
    ls [-ABCFGHLOPRSTUW@abcdefghiklmnopqrstuwx1] [file ...]
DESCRIPTION
    For each operand that names a file of a type other than directory, ls displays its name as well as
    any requested, associated information.  For each operand that names a file of type directory, ls
    displays the names of files contained within that directory, as well as any requested, associated
    information.

Cheat Sheet

Another Cheat Sheet