On the paragraph explaining arithmetic expansion, Bash’s user guide uncovers 2 different ways of evaluating an expression, the first one uses $(( EXPRESSION )) and the second one uses $[ EXPRESSION ]. The two ways seem pretty similar as the only difference I have found is:
$[ EXPRESSION ]will only calculate the result of EXPRESSION, and do no tests:
Yet, I am intrigued because the same document recommends using $[ EXPRESSION ] rather than $(( EXPRESSION )).
Wherever possible, Bash users should try to use the syntax with square brackets:
Why would you want that if less tests are being done?
Answers:
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Method 1
Duplication Question (with answer)
https://stackoverflow.com/questions/2415724/bash-arithmetic-expression-vs-arithmetic-expression
The manpage for bash v3.2.48 says:
[…] The format for arithmetic expansion is:
$((expression))The old format $[expression] is deprecated and will be removed in upcoming versions of bash.
So $[…] is old syntax that should not be used anymore
In addition to that answer:
http://manual.cream.org/index.cgi/bash.1#27
Info relating to bash versions:
Here is some info about bash man pages (its hard to find info on what version each one is referring to):
OPs link:
http://www.tldp.org/guides.html
Bash Guide for Beginners
version: 1.11
author: Machtelt Garrels,
last update: Dec 2008
sth (74.6k rep) quoting bash v3.2.48
from https://stackoverflow.com/questions/2415724/bash-arithmetic-expression-vs-arithmetic-expression)
Note: More info about [] vs (()) here: http://lists.gnu.org/archive/html/bug-bash/2012-04/msg00033.html
a link I found:
http://www.gnu.org/software/bash/manual/
last updated August 22, 2012
http://www.gnu.org/software/bash/manual/bash.html#Arithmetic-Expansion
All methods was sourced from stackoverflow.com or stackexchange.com, is licensed under cc by-sa 2.5, cc by-sa 3.0 and cc by-sa 4.0