Bash Shell Programming from the Ground Up

pwd, ls, cd, echo; tilde (~), .. and .

metacharacters: | & ; < > space tab newline
and: ~ $ #

strong quoting - single quotes protect everything between them from the shell

weak quoting - double quotes protect everything except the $, the backslash (\) and (not so relevant) the back quotes (``)

backslash - protects the next character from the shell

(Not so) special case: Filenames and strings containing spaces (and potentially) other weird characters.

simple commands, control operators: || & && ; ;; ;& ;;& | |& <newline>

brace expansion, tilde expansion, parameter/variable expansion, command substitution, arithmetic expansion, filename expansion, quote removal

Every program:

• - reads input from its standard input channel (stdin, 0 - usually the keyboard),

• - writes its output to the standard output channel (stdout, 1 - usually the screen)

• - sends error messages to the standard error channel (stderr, 2 - usually also the screen).

All channels can be directed elsewhere (or even closed).

Pipes and other redirections in action. Use |& to redirect both stdout and stderr into a pipeline.