Ubuntu Linux Toolbox: 1000+ Commands for Power Users, 2nd Edition

B

Shell Special Characters and Variables

IN THIS APPENDIX

Using special shell characters

Using shell variables

Ubuntu provides bash as the default shell. Chapter 3 helps you become comfortable working in the shell. This appendix provides a reference to the numerous characters and variables that have special meaning to the bash shell. Many of those elements are referenced in Table B-1 (“Shell Special Characters”) and Table B-2 (“Shell Variables”).

Using Special Shell Characters

You can use special characters from the shell to match multiple files, save some keystrokes, or perform special operations. Table B-1 shows some shell special characters you may find useful.

Table B-1: Shell Special Characters

Character	Description
*	Match any string of characters.
?	Match any one character.
‘ … ’	Remove special meaning of characters between quotes. Variables are not expanded.
“ … ”	Same as simple quotes except for the escape characters ($, `, and \) that preserve their special meaning. Variables are expanded.
\	Escape character to remove the special meaning of the character that follows.
~	Refers to the $HOME directory.
~+	Value of the shell variable PWD (working directory).
~-	Refers to the previous working directory.
.	Refers to the current working directory.
..	Refers to the directory above the current directory. Can be used repeatedly to reference several directories up.
$param	Used to expand a shell variable parameter.
cmd1`cmd2`or cmd1$ (cmd2)	cmd2 is ...