The Perl Short Questions Megathread: executable line noise

The Something Awful Forums > Discussion > Serious Hardware/Software Crap > The Cavern of COBOL > The Perl Short Questions Megathread: executable line noise

Kakesu: Nov 4, 2005; ETHICAL.

I have an incredibly annoying problem that is completely stumping myself and some other perl users at work, that I'm really hoping somebody can help with. I'm using ActivePerl in windows, and the script in question is designed to run a build process automatically. The script runs on two separate PCs, alternating back and forth so that there's a constant stream of new builds. None of this is really relevant to the problem, but I thought some background would be nice.

The problem is this: at one point in the script, the Windows "mkdir" command is called using a system() call. On ONE MACHINE ONLY, this fails, regardless of the location of the directory that is being created. The other machine executes the command just fine. The actual script creates a directory on another machine over the network, but I've tested it with local directories, and the same failure happens. Running the mkdir from a Windows command prompt works fine in both cases.

The line of code in question is this:

code:

system("mkdir \"\\\\machine-name\\shared_directory\\directory_to_create\"");

From my testing, it appears that the backslashes in the path aren't all escaping properly. The error that is thrown indicates that perl is trying to run the following command when this is run:

code:

mkdir "\\machine-name\\shared_directory\\directory_to_create"

The first backslashes escape as they're supposed to, but the ones later on in the path don't. Just for shits and giggles, I tried replacing those with single backslashes in the script, and got the following:

code:

mkdir "\\machine-nameshared_directory\directory_to_create"

The second set disappears completely, but the third displays the way that we originally wanted it to (even though it shouldn't).

We've tried re-installing Perl, using a different version of Perl, rechecking permissions, etc. Nothing seems to make any difference. Has anyone seen anything similar to this before, or have any ideas why a string that would be parsed normally on one machine, would be parsed completely differently on another machine running an identical Perl install?

# ¿ Dec 11, 2007 22:22

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# ¿ May 2, 2024 03:54

Kakesu: Nov 4, 2005; ETHICAL.

Triple Tech posted:

For starters, don't make shell calls if there are CPAN modules available to do the same thing. There should definitely be an ActiveState-approved module that creates file paths...

Two, the system function accepts arrays! The first argument to the function is the command you want to run and subsequent arguments are arguments to the command, properly and automatically escaped by Perl.

So, you should try to write out your system call (which you shouldn't be using) like this:
code:
system('mkdir', $dirname);
And you can test if you have the correct number of slashes by just printing $dirname to STDOUT. That or just use forward slashes (no escaping necessary).

Thanks. Right after I posted that, we found another Perl user that explained that we could just use mkdir on its own, without a shell call, and that seems to be working.

Still no idea why it stopped working, though. The thing I forgot to mention in my original post is that this script has been running continuously for the past 3 months, but this is the first time it's failed like this. Very strange.

# ¿ Dec 11, 2007 22:42

The Something Awful Forums > Discussion > Serious Hardware/Software Crap > The Cavern of COBOL > The Perl Short Questions Megathread: executable line noise