Re: Simple Perl "Shell" Script on Windows XP to Run Multiple, Simultaneous Processes in Parallel

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Re^2: Simple Perl "Shell" Script on Windows XP to Run Multiple, Simultaneous Processes in Parallel by Jim (Curate) on Jul 29, 2009 at 23:07 UTC
I think you may have misread my question. The first thing I tried was `perldoc -f system` at the command prompt. The `system(1, ...)` idiom is not documented there as one would expect it to be. I then searched the World Wide Web using both Google and Google Code Search. Neither of these search techniques was fruitful. Another respondent pointed me to the following explanation in `perldoc perlport`, which is laconic and difficult to understand if, like me, you don't already fully understand the language feature being "documented": `system` [download] `As an optimization, may not call the command shell specified in $ENV{PERL5SHELL}. system(1, @args) spawns an external process and immediately returns its process designator, without waiting for it to terminate. Return value may be used subsequently in wait or waitpid. Failure to spawn() a subprocess is indicated by setting $? to "255 << 8". $? is set in a way compatible with Unix (i.e. the exitstatus of the subprocess is obtained by "$?>> 8", as described in the documentation). (Win32)` In fact, I'm prepared now to argue that `system(1, ...)` isn't properly documented at all. When I click on the Google search link you included in your post, I don't get the results you described at all. The URL http://perldoc.perl.org/functions/system.html doesn't show up on the first page of results at all. But it doesn't matter because my question isn't answered in `perldoc -f system` (i.e., `perldoc perlfunc`) anyway. Jim	[reply] [d/l] [select]

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Re^2: Simple Perl "Shell" Script on Windows XP to Run Multiple, Simultaneous Processes in Parallel
by Jim (Curate) on Jul 29, 2009 at 23:07 UTC

I think you may have misread my question.

The first thing I tried was perldoc -f system at the command prompt. The system(1, ...) idiom is not documented there as one would expect it to be.

I then searched the World Wide Web using both Google and Google Code Search. Neither of these search techniques was fruitful.

Another respondent pointed me to the following explanation in perldoc perlport, which is laconic and difficult to understand if, like me, you don't already fully understand the language feature being "documented":

system
[download]

As an optimization, may not call the command shell specified in $ENV{PERL5SHELL}. system(1, @args) spawns an external process and immediately returns its process designator, without waiting for it to terminate. Return value may be used subsequently in wait or waitpid. Failure to spawn() a subprocess is indicated by setting $? to "255 << 8". $? is set in a way compatible with Unix (i.e. the exitstatus of the subprocess is obtained by "$?>> 8", as described in the documentation). (Win32)

In fact, I'm prepared now to argue that system(1, ...) isn't properly documented at all.

When I click on the Google search link you included in your post, I don't get the results you described at all. The URL http://perldoc.perl.org/functions/system.html doesn't show up on the first page of results at all. But it doesn't matter because my question isn't answered in perldoc -f system (i.e., perldoc perlfunc) anyway.

Jim

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