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Top Forums Shell Programming and Scripting AIX function example with "shift" command Post 302900103 by Scrutinizer on Sunday 4th of May 2014 09:42:07 AM
Old 05-04-2014
By using shift, $1 becomes $2, $2 becomes $3, etc.. in the following line:
Code:
  print -u2 "$prog: usage: $prog $@"

there is "$@" which stands for all parameters which originally would have been all parameters to the function, but because of the shift it has become parameters $2, $3, etc of the original parameters to the function.

Programmatically I do not really see what the purpose is in this case, since they could also have used:

Code:
function usage
{
  print -u2 "$1: usage: $@"
  exit 1
}

But I would have to say the original is easier to read and understand, so that may be the reason..

The other thing - it prints to stderr - is logical since the usage is often printed when a user uses a wrong syntax.

Last edited by Scrutinizer; 05-04-2014 at 10:50 AM..
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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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