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Full Discussion: Loop Counting Question
Top Forums UNIX for Dummies Questions & Answers Loop Counting Question Post 302747149 by phunk on Thursday 20th of December 2012 04:32:49 PM
Old 12-20-2012
Loop Counting Question

I figured this out, but I wanted to pose the question.

I was writing a while loop that required counting the amount of times the job had run, for example.

An example below is what I had:

Code:
variable=0

while :
do
    variable = `expr $variable + 1`
done

That didn't do what I needed it to (allow multiple attempts of input). However the following did:

Code:
variable=0

while :
do
    (( variable = variable + 1 ))
done

I was just curious why the double parenthesis handled that while the expr statement didn't. I'm still learning Smilie
 

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IO::Async::Signal(3pm)					User Contributed Perl Documentation				    IO::Async::Signal(3pm)

NAME
"IO::Async::Signal" - event callback on receipt of a POSIX signal SYNOPSIS
use IO::Async::Signal; use IO::Async::Loop; my $loop = IO::Async::Loop->new; my $signal = IO::Async::Signal->new( name => "HUP", on_receipt => sub { print "I caught SIGHUP "; }, ); $loop->add( $signal ); $loop->run; DESCRIPTION
This subclass of IO::Async::Notifier invokes its callback when a particular POSIX signal is received. Multiple objects can be added to a "Loop" that all watch for the same signal. The callback functions will all be invoked, in no particular order. EVENTS
The following events are invoked, either using subclass methods or CODE references in parameters: on_receipt Invoked when the signal is received. PARAMETERS
The following named parameters may be passed to "new" or "configure": name => STRING The name of the signal to watch. This should be a bare name like "TERM". Can only be given at construction time. on_receipt => CODE CODE reference for the "on_receipt" event. Once constructed, the "Signal" will need to be added to the "Loop" before it will work. AUTHOR
Paul Evans <leonerd@leonerd.org.uk> perl v5.14.2 2012-10-24 IO::Async::Signal(3pm)
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