[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: [Help-bash] Definitive answer of the difference between [ and [[
|
From: |
Peg Russell |
|
Subject: |
Re: [Help-bash] Definitive answer of the difference between [ and [[ |
|
Date: |
Sat, 1 Feb 2014 22:22:38 +0000 (UTC) |
|
User-agent: |
Loom/3.14 (http://gmane.org/) |
> I'm wondering what the difference is between [ and [[. After reading
> the manual, it is not clearly to me that I know all the differences
> between them without missing anything. There are some online
> discussions. But they are not definitive. Does anyone have a
> definitive answer to this question? Thanks.
They are two ways to evaluate a bash expression. [ is a shell builtin (type
-a [) and is a synonym for the test builtin. [[ is a keyword (type -a [[).
Besides the man page and reference there is the help builtin command. To see
a brief list of operators valid for both, type: help test. I think the two
links below could be helpful.
What is the difference between test, [ and [[ ?
http://mywiki.wooledge.org/BashFAQ/031
How to use double or single bracket, parentheses, curly braces
http://stackoverflow.com/questions/2188199/how-to-use-double-or-single-bracket-parentheses-curly-braces
Peg Russell