Linux Shell

• Standard

Standard	Version	Description
POSIX 1003.2(ISO/IEC 9945-2)	1992, 1988	the shell and the standard utilities
POSIX 1003.2a (User Portability Extensions, UPE)		standards of interactive shell use and interactive utilities like the vi editor

• Linux Shell Scripting Tutorial v1.05r3 - A Beginner's handbook
• Shell Command Language Index
• UNIX Shell Script Tutorials & Reference
• An Introduction To Shell Programming
• UNIX Power Tools
• Scripts大集合

• nash

• Bash
  • Bash Reference Manual, Bash Reference Manual
  • Learning the bash Shell, 3rd, Fulltext, Learning the bash Shell, 3rd Safari, Learning the bash Shell, 2nd, Fulltext
  • BASH Programming - Introduction HOWTO
  • Advanced Bash-Scripting Guide
    • Chapter 6. Exit and Exit Status
    • Appendix D. Exit Codes With Special Meanings

• Korn Shell
  • Learning the Korn Shell

• sash(Stand-alone shell)

Features

Feature	Syntax	Description	Contributor
variable assignment	varname=value
environment variable	export varname or export varname=value	varname=value command for variables to be in the environment of a particular subprocess (command) only
brace expansion		For example, a{b,c} becomes ab ac	C shell
tilde(~) expansion			C shell
variable substitution(variable expansion or parameter substitution)	$varname or ${varname}
command substitution	$(…) or `…`
arithmetic expression(arithmetic expansion)	$((…)) or `expr …` or let … or ((…))
pathname expansion(wildcard expansion or filename expansion)	* or ? or […]
process substitute	<(list) or >(list)
condition test	[...] or test …	tests whether the exit status of a list of commands is 0 (since 0 means "success" by UNIX convention)
extended condition test	[[...]]	No filename expansion or word splitting takes place between [[ and ]], but there is parameter expansion and command substitution	Korn shell
arithmetic condition test	((…)) or let …	return an exit status of 0 if the arithmetic expressions they evaluate expand to a non-zero

Command

Command	Description	Examples
set	When set has arguments, the arguments are assigned to the position parameters.	set “first” “second” “third”
colon ":"	No effect; the command does nothing beyond expanding arguments and performing any specified redirections. Otherwise, the expanding arguments will be considered as command to execute. A zero exit code is returned.