Learning the Command Line

This list is focused on helping people learn how to use a command line interface. You may have seen or heard about the shell, sh, bourne, prompt, terminal, console, Bash, scripts or even batch files. I hope the following links will help fill in the gaps between what you know and what you want to learn.

The main URL for this page is https://www.grantbow.com/command_line.html. It was started in October 2011. Thank you to all the contributors who have helped me keep this page updated. Email is encouraged to Grant Bowman <grantbow@grantbow.com>

Editing a web page on a web hosting provider is a common need. Putting together a few things described here makes this quick and easy.

1. Find the terminal on your computer and issue the command

   ssh user@host

   . A password or ssh key will authenticate you. Then you are given a prompt.
2. Type

   $ screen

   to keep the connection alive if you are disconnected. This also allows running multiple terminals simultaneously.
   • This will look like nothing happened but something good happened.
   • The code to make screen pay attention is <ctrl-a>
   • So the command to get help from screen looks like <ctrl-a> ?
3. Type basic commands like

   ls -l

   , and

   cd

   to determine what file to edit. The pages of your website will be arranged just like the files of your website.
4. Type

   vi <filename>

   to edit the file.
   • This editor uses modes. Move around in the file using

     hjkl

     , delete characters with

     x

     .
   • insert using

     i

     to begin inserting characters in insert mode.
   • Return to normal mode using

     <esc>

     .
   • A colon starts a command you can type instead of a single character. Save the file with

     :w

     .
5. Verify results by reloading the web page in your web browser. Congratulations!

I stand on the backs of giants in talking about command line computer use, especially my favorite interpreter, BASH available on many platforms. I am very grateful to be working with Dreamfish and thankful to participate in the libera.chat IRC Network.

A script is simply a text file with commands in it. It is run as if you were typing them. It is real programming. Here is the canonical example:

#!/bin/bash
echo "Hello World!"

How about 2>&1, what kind of magic incantation is this? These are called file descriptors. 0 means standard input, 1 means standard output and 2 means standard error. So copy the errors to the address of the output. Then you can write to a file with > file.txt or append to a file using >> file.txt

First Commands

Finding the Terminal!

Next steps

Please email inquiries & suggestions to Grant Bowman <grantbow@grantbow.com>

Last update: 20230829