6.1. Bash

This section is a summary of the most common Bash commands to serve as a general introduction or refresher to help newer Linux users, or those who have not used it in some time.

Interested in learning even more about Bash? The GNU Bash Reference is an amazing resource!

Common Commands

$ ls

Lists the contents in the current directory.

Example:

[you@metis.niu.edu ~]$ ls
bin examples 

Common Arguments:

• -a

  Prints everything, including hidden files.

  Example:

  [you@metis ~]$ ls -a
  .              .dbus           .kde
  ..             .dotnet         .kshrc   
  .bash_history  .emacs          .local           
  .bash_logout   .esd_auth       .mozilla       
  .bash_profile  examples        .ssh       
  .bashrc        .gitconfig      .wget-hsts      
  bin            .nv             .Xauthority
  .cache         .python_history .xemacs
  .config        .jupyter        .zshrc
  

Command Manual

$ cd <path>

Changes the current directory to the specified path.

There are a few types of paths in a Unix-based filesystem, mainly being:

• Absolute Path

  Absolute paths always lead to the same location, no matter the context they are interpreted from.

  They typically start with /, which is the root (base level) of the filesystem, but they can also start with ~, which is your home directory.

  For example, your home directory (akin to a desktop in a graphical OS) is at /home/you or ~.

• Relative Path

  Relative paths are dependent on where they are run from, and are specified by not starting with a /.

  For example, if you are in your home directory, the bin directory can be referenced by ./bin.

  The . signifies "current directory", but you can also use "..", which would represent "up one directory".

Here is an example of changing to your bin directory based on an absolute path:

[you@metis ~]$ cd /home/you/bin
[you@metis bin]$

(cd ~/bin would be equivalent!)

Changing directory to your bin directory relative to your current directory (that being ~):

[you@metis ~]$ cd bin
[you@metis bin]$

(cd ./bin would be equivalent!)

Going up a directory, then into the examples directory:

[you@metis bin]$ cd ../examples
[you@metis examples]$

Command Manual

$ touch <file_name | file_name>

Creates a new file with empty contents.

Example:

[you@metis ~]$ touch hello.txt
[you@metis ~]$ ls
bin projects hello.txt

Command Manual

$ nano <file_name | file_path/file_name>

A simplistic terminal file editor, useful for quick edits.

Shouldn't be used for large files; instead, you should use emacs, vim, or ideally, an editor on your machine with remote SSH capability. See Chapter 1.1 for more information on setting up Visual Studio Code, a popular option.

Example:

[you@metis ~]$ touch hello.txt
[you@metis ~]$ nano hello.txt

Command Manual

$ mkdir <dir_name | dir_path/dir_name>

Creates a new and empty directory.

Example:

[you@metis.niu.edu ~]$ mkdir hello
[you@metis.niu.edu ~]$ ls
bin examples hello

Command Manual

$ export <var>=<string | expression>

Sets an environment variable. Unless somehow preserved, these will be cleared when you close the session!

Example:

[you@metis.niu.edu ~]$ export FOO="bar"

Command Manual

$ echo <string | expression>

Outputs the specified string or expression to stdout (the terminal).

You can output environment variables by prefacing a variable name with $.

Example:

[you@metis.niu.edu ~]$ echo "Hello, Metis!"
Hello, Metis!
[you@metis.niu.edu ~]$ export FOO="Hello, Metis!"
[you@metis.niu.edu ~]$ echo "$FOO"
Hello, Metis!

Command Manual

Help Commands

Should you feel confused on the usage of any command, you can print additional helpful information on many commands!

The 5 common ways to print help on a command, in order of the density of information output:

• $ info <command>
• $ man <command>
• $ <command> --help
• $ <command> -h
• $ <command> -?

Generally, first try $ <command> --help, and if you're still confused, try $ man <command>.