Linux Command Line and Shell Scripting Bible, 5th Edition

APPENDIX AQuick Guide to Bash Commands

IN THIS APPENDIX

• Reviewing built-in commands
• Looking at common Bash commands
• Assessing environment variables

As you’ve seen throughout this book, the Bash shell contains lots of features and thus has lots of commands. This appendix provides a concise guide to allow you to quickly look up a feature or command that you can use from the Bash command line or from a Bash shell script.

Reviewing Built-In Commands

The Bash shell includes many popular commands built into the shell. You can use these commands to achieve faster processing times. Table A.1 shows the built-in commands available directly from the Bash shell.

Table A.1 Bash Built-In Commands

Command	Description
&	Starts a job in background mode.
((x))	Evaluates the x mathematical expression.
not:	Reads and executes commands from a designated file in the current shell.
:	Does nothing and always exits successfully.
[t]	Evaluates the t conditional expression.
[[e]]	Evaluates the e conditional expression.
alias	Defines an alias for the specified command.
bg	Resumes a job in background mode.
bind	Binds a keyboard sequence to a readline function or macro.
break	Exits from a for, while, select, or until loop.
builtin	Executes the specified shell built-in command.
caller	Returns the context of any active subroutine call.
case	Selectively executes commands based on pattern.
cd	Changes the current directory to the specified directory.
command	Executes ...