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Full Discussion: POSIX compliance...
Operating Systems OS X (Apple) POSIX compliance... Post 302976886 by Don Cragun on Thursday 7th of July 2016 02:24:13 PM
Old 07-07-2016
Some shells (such as bash and 1993 or later versions of ksh) provide:
Code:
for((n=1; n<=100; n++))
do	echo "process n=$n"
done

but this is an extension that is not yet specified by the standards. As you said, standard ways to do the same thing require an initialization step before the loop, such as in:
Code:
n=1
while [ $n -le 100 ]
do	echo "process n=$n"
	n=$((n + 1))
done

and in:
Code:
n=0
while [ $((++n <= 100)) -eq 1 ]
do	echo "process n=$n"
done

Note: As noted by Scrutinizer in post #8, the POSIX standards do not require $((++n)) to work. (It works with a recent bash and with a 1993 or later version of ksh, but is an extension to the requirements specified by the standards.)
Code:
n=0
while [ $(((n += 1) <= 100)) -eq 1 ]
do	echo "process n=$n"
done

should work in an POSIX-conforming shell.

Last edited by Don Cragun; 07-10-2016 at 04:56 PM.. Reason: Add note.
This User Gave Thanks to Don Cragun For This Post:
 

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IO::Async::Timer::Absolute(3pm) 			User Contributed Perl Documentation			   IO::Async::Timer::Absolute(3pm)

NAME
"IO::Async::Timer::Absolute" - event callback at a fixed future time SYNOPSIS
use IO::Async::Timer::Absolute; use POSIX qw( mktime ); use IO::Async::Loop; my $loop = IO::Async::Loop->new; my @time = gmtime; my $timer = IO::Async::Timer::Absolute->new( time => mktime( 0, 0, 0, $time[4]+1, $time[5], $time[6] ), on_expire => sub { print "It's midnight "; $loop->stop; }, ); $loop->add( $timer ); $loop->run; DESCRIPTION
This subclass of IO::Async::Timer implements one-shot events at a fixed time in the future. The object waits for a given timestamp, and invokes its callback at that point in the future. For a "Timer" object that waits for a delay relative to the time it is started, see instead IO::Async::Timer::Countdown. EVENTS
The following events are invoked, either using subclass methods or CODE references in parameters: on_expire Invoked when the timer expires. PARAMETERS
The following named parameters may be passed to "new" or "configure": on_expire => CODE CODE reference for the "on_expire" event. time => NUM The epoch time at which the timer will expire. Once constructed, the timer object will need to be added to the "Loop" before it will work. Unlike other timers, it does not make sense to "start" this object, because its expiry time is absolute, and not relative to the time it is started. AUTHOR
Paul Evans <leonerd@leonerd.org.uk> perl v5.14.2 2012-10-24 IO::Async::Timer::Absolute(3pm)
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