Quick Reference

cat

cat is a command that concatenates files and prints the concatenated files to the standard output.

$ echo "This is an:" > beginning.txt
$ echo "example" > end.txt
$ cat beginning.txt end.txt
This is an:
example

cd

cd is used to change directory. Unlike most commands, cd is not a separate program, it is a shell built-in. cd is a useful tool to navigate up and down the hierarchy of the file systems on your machine, and move into a given directory.

$ cd ~
$ cd /home

cp

cp is used to copy files or directories.

$ cp source destination
$ cp file1.txt file2.txt
$ cp -b file1.txt file2.txt
$ cp -v file1.txt file2.txt
$ cp * ~/Desktop

echo

echo is used to output whatever it is given into stdout. Often useful see the value of environment variables.

$ echo "Hello World!"
Hello World!
$ echo $USER
<your username>

ls

ls is used to list the contents of a directory. By default, ls will simply print file names.

$ ls
directory file

man

man allows users to format/display the user “manual” that is built into Linux. This manual holds a catalogue of commands and other aspects of the Linux OS.

$ man [command]
$ man ls
$ man strcmp

mkdir

mkdir is used to create directories (if they do not already exist) on a file system.

The general format is

$ mkdir [options] directories

mv

mv is used to move a source file or directory into a destination directory. It is also commonly used to rename files.

$ mv source desination

passwd

passwd is a command that is used to change the password of system users.

$ passwd
Changing password for user [current user]
(current) UNIX password:
Enter new UNIX password:
Retype new UNIX password:
passwd: password updated successfully

pwd

pwd stands for print working directory. pwd outputs the full pathname of the current work directory.

$ pwd
/home/bo/Desktop

pwd can also be used to store the full path to the current directory.

x=$(pwd)

rm

rm is used to delete one or multiple files from your current directory. Be careful when using because this does not move the item to trash, it permanetly deletes it.

$ rm file1.txt file2.txt

rmdir

rmdir is used to remove empty directories.

The format is

$ rmdir [options] directories

> (standard output redirection operator)

command1 -[options] [arguments] > <output file name>

The standard output redirection operator is used in bash to redirect the output of one command to a specified file.

./a.out > output.txt

>>

‘>>’ is a shell operator that you can use to append the output in an existing file.

$ echo line 1 >> example.txt
$ cat example.txt
line 1
$ echo line 2 >> example.txt
$ cat example.txt
line 1
line 2