Getting to grips with the shell

1
Getting to grips with the shell

• An introduction to the UNIX shell.
• Graham Bleach, Feb 2006

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Overview

• What is a shell?
• Why would I need to use the shell?
• How do I use it?

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What is the shell?

• The outer layer of the OS
• Nearest the user
• Interactive
• Often means the UNIX command line.
• There are other sorts of shell.
• Bash, the Bourne-Again Shell.

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Why use it?

• Some things impossible with a GUI.
• You can automate things.
• Can be faster than using a GUI.
• Text commands are repeatable.

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Getting started

• Open a terminal emulator.
• Run a command.
• Use the up/down arrows to repeat commands and
  correct mistakes.

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Basic navigation

• Display your current directory with pwd.
• List files with ls
• Use cd to change directory.
• Show file contents with cat.
• Or, more usefully with less.

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Saving time

• Too much typing is a waste of time.
• Tab completion
• On command names
• On file names.
• Reverse search (Ctrl-r).

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Saving output

• We can save the output of a command using gt
• Example Finding lines which say Bleach
• Be careful not to write back over the file you
  started with

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Doing more than one thing

• Using temporary files is messy and slow.
• Commands can be connected to each other using
  pipes.
• command1 command2
• e.g dmesg less

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Scripting

• Putting commands that we typed interactively into
  a file.
• At the top of the file we need !/bin/bash

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Finding out more

• Manual pages
• apropos
• man
• whatis.
• Advanced bash scripting guide.
• Think UNIX, Jon Lasser.
• Mailing list.