Comments on: Which comparator, test, bracket, or double bracket, is fastest?

By: bun

bun — Thu, 12 Nov 2009 02:56:41 +0000

$ though the diff in speed between [ and ‘test’ is significant in iteration, it’s trivial compared to the use of [[ since bash doesn’t perform path expansion & word splitting, other expansions (var, arith, …) are still performed

By: Six ways to speed up your shell scripts

Six ways to speed up your shell scripts — Sat, 22 Mar 2008 03:52:39 +0000

[...] reading Shell Scripting Recipes, I became more interested in the speed of shell operations. In his book, Chris shows says “Command Substitution Is Slow.” He is [...]

By: admin

admin — Fri, 25 Jan 2008 00:08:05 +0000

Can Bican,

Although its not related to the speed, that is a very good article as many admins do not work in as homogeneous environments as myself.

Thanks for the link!

By: admin

admin — Fri, 25 Jan 2008 00:05:57 +0000

eliott,

Good point. I thought about that, but figured since they all can be used that way and it would be cached, it was a valid test.

However, if the single bracket performs better in string comparisons, that should be noted as well.

By: eliott

eliott — Thu, 24 Jan 2008 19:33:37 +0000

Interesting.

It probably isn’t good that you are doing stat calls on the filesystem (even though they are cached) for your test though.

Doing string comparison may be a better example.

$ time for i in {1..100000}; do [[ "foo" = "foo" ]]; done
real 0m1.386s
user 0m1.368s
sys 0m0.016s

$ time for i in {1..100000}; do [ "foo" = "foo" ]; done
real 0m1.957s
user 0m1.904s
sys 0m0.052s

By: Can Bican

Can Bican — Thu, 24 Jan 2008 07:46:23 +0000

Not really related, but here is another discussion about compatibility of test operations:

http://www.linuxtopia.org/online_books/linux_development_tools/libtool_autoconf_automake_book/autobook_216.html