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Top Forums Shell Programming and Scripting Is there a way to make bash [or another shell] use all CPU cores to execute a single script? Post 302389944 by pludi on Tuesday 26th of January 2010 12:34:20 PM
Old 01-26-2010
If you want to benchmark a system, use a language with less run-time overhead like C, especially if you're just burning CPU.

As for your question: no, shells don't do multi-thread by themselves (I'm assuming you mean "shells" not "OS", since most OS use all cores anyways). Why should they. A shell is designed to interact with a user who (more or less) knows what he/she does. That they're scriptable is a nice value-adding feature.

Besides, how should the shell divine what parts of your program can run in parallel and which can't? What variables should be shared across threads? How should it avoid deadlocks? That stuff has (as of yet) to be considered by a programmer, and those can usually handle backgrounded subshells and a wait call or two.

P.S.: There is no such thing as an "overloaded CPU". A CPU can be in (almost) any state between "idle" and "completely utilized", but that's it.
 

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less(3pm)						 Perl Programmers Reference Guide						 less(3pm)

NAME
less - perl pragma to request less of something SYNOPSIS
use less 'CPU'; DESCRIPTION
This is a user-pragma. If you're very lucky some code you're using will know that you asked for less CPU usage or ram or fat or... we just can't know. Consult your documentation on everything you're currently using. For general suggestions, try requesting "CPU" or "memory". use less 'memory'; use less 'CPU'; use less 'fat'; If you ask for nothing in particular, you'll be asking for "less 'please'". use less 'please'; FOR MODULE AUTHORS
less has been in the core as a "joke" module for ages now and it hasn't had any real way to communicating any information to anything. Thanks to Nicholas Clark we have user pragmas (see perlpragma) and now "less" can do something. You can probably expect your users to be able to guess that they can request less CPU or memory or just "less" overall. If the user didn't specify anything, it's interpreted as having used the "please" tag. It's up to you to make this useful. # equivalent use less; use less 'please'; "BOOLEAN = less->of( FEATURE )" The class method "less->of( NAME )" returns a boolean to tell you whether your user requested less of something. if ( less->of( 'CPU' ) ) { ... } elsif ( less->of( 'memory' ) ) { } "FEATURES = less->of()" If you don't ask for any feature, you get the list of features that the user requested you to be nice to. This has the nice side effect that if you don't respect anything in particular then you can just ask for it and use it like a boolean. if ( less->of ) { ... } else { ... } CAVEATS
This probably does nothing. This works only on 5.10+ At least it's backwards compatible in not doing much. perl v5.18.2 2013-11-04 less(3pm)
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