Windows 7: fork in perl script spawns new cmd window

mpeppler has asked for the wisdom of the Perl Monks concerning the following question:

Hi,

I've just got a new Windows 7 laptop at work - running this little script:

open(IN, "svn info c:/path/to/file |");
@l = <IN>;

foreach (@l) {
    print "$_";
}
[download]

opens a new cmd window which runs the svn info command instead of being able to read the output in the script.

This doesn't happen on other W7 machines around here, so I'm guessing this is a config issue somewhere - but my Windows admin know-how is essentially inexistent....

Any constructive suggestion (so "switch to linux" is not an option :-)) welcome!

Michael

Comment on Windows 7: fork in perl script spawns new cmd window Download Code

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Re: Windows 7: fork in perl script spawns new cmd window by BrowserUk (Patriarch) on Jan 25, 2013 at 17:13 UTC
Compare the settings of `path`, `assoc .pl` & `ftype perl` on the two machines. Therein (almost certainly) lies a difference; and explanation of the different behaviour. Also, you can probably dodge the issue by using the full path of the svn command. With the rise and rise of 'Social' network sites: 'Computers are making people easier to use everyday' Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error. "Science is about questioning the status quo. Questioning authority". In the absence of evidence, opinion is indistinguishable from prejudice.	[reply] [d/l] [select]
Re: Windows 7: fork in perl script spawns new cmd window by mpeppler (Vicar) on Jan 25, 2013 at 09:51 UTC
OK - so adding "call" like so `open(IN, "call svn info ... \| ");` [download] fixes the problem - but I'd still like to understand why this is needed in this new environment, and isn't needed on other W7 machines or older XP machines around here. Michael	[reply] [d/l]
Re^2: Windows 7: fork in perl script spawns new cmd window by Anonymous Monk on Jan 25, 2013 at 10:08 UTC
Probably one calls the shell, and the other doesn't, see system/open and perl -V:sh Related perlrun Behind the GUI lives the Shell Windows Command Line Interpreter\|Shell\|DOS Prompt\|Batch Files\|Scripting Csh Programming Considered Harmful How Command Line Parameters Are Parsed http://www.gnu.org/software/bash/manual/bashref.html#Quoting String::ShellQuote/Win32::ShellQuote, Re: system() implementation on Windows (again), Re^3: system() implementation on Windows (again), Everyone quotes command line arguments the wrong way Proc::Background The Windows NT Command Shell exec always invokes the shell? win32, System, exec different behaviour with spaces	[reply]
Re^3: Windows 7: fork in perl script spawns new cmd window by mpeppler (Vicar) on Jan 25, 2013 at 13:01 UTC
It's from the exact same code, same build of perl 5.14, etc. The actual code uses IO::CaptureOutput, FWIW... Michael	[reply]
Re^4: Windows 7: fork in perl script spawns new cmd window by MidLifeXis (Monsignor) on Jan 25, 2013 at 13:36 UTC
Re^5: Windows 7: fork in perl script spawns new cmd window by mpeppler (Vicar) on Jan 25, 2013 at 15:10 UTC
Re: Windows 7: fork in perl script spawns new cmd window by Anonymous Monk on Jan 25, 2013 at 09:30 UTC
mine neither, try `use Win32 qw(SW_HIDE); Win32::SetChildShowWindow(SW_HIDE);`	[reply] [d/l]
Re: Windows 7: fork in perl script spawns new cmd window by Anonymous Monk on Jan 26, 2013 at 21:54 UTC
Switching to Linux is a perfectly cromulent suggestion.	[reply]
Re^2: Windows 7: fork in perl script spawns new cmd window by topher (Scribe) on Jan 28, 2013 at 22:54 UTC
Agreed. Using Linux embiggens even the smallest program.	[reply]
Re: Windows 7: fork in perl script spawns new cmd window by mpeppler (Vicar) on Jan 30, 2013 at 11:32 UTC
So - here's the cause for the problem - in case someone else runs into something similar in the future. The svn.exe binary was included in a directory that has elevated execution rights associated through a policy. The perl binary is not in that same directory, so Win7's kernel refused to run the svn command in the same process space. Moving the svn binary out of this directory, or moving the perl tree into this directory resolves the problem. Michael	[reply]


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