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System, exec different behaviour with spaces

by sacambs (Initiate)
on Jan 12, 2012 at 09:53 UTC ( #947507=perlquestion: print w/ replies, xml ) Need Help??
sacambs has asked for the wisdom of the Perl Monks concerning the following question:

I'm seeing some odd behaviour when running an exec command on an executable whose path contains spaces, for some reason part of the command name seems to be passed as an argument to the program. Oddly this doesn't happen if I use system instead of exec. The docs for exec suggest that since I'm passing an argument list there should be no shell interpretation, so I can't figure out why this would be happening.

>perl -e "exec 'c:\Program Files\Java\jdk1.5.0_22\bin\java.exe','-vers +ion'" D:\Subversion\FastQC\bin>Exception in thread "main" java.lang.NoClassD +efFoundError: Files\Java\jdk1/5/0_22\bin\java/exe >perl -e "system 'c:\Program Files\Java\jdk1.5.0_22\bin\java.exe','-ve +rsion'" java version "1.5.0_22" Java(TM) 2 Runtime Environment, Standard Edition (build 1.5.0_22-b03) Java HotSpot(TM) 64-Bit Server VM (build 1.5.0_22-b03, mixed mode)
The java error from the exec shows that the correct binary is being called, but that its first argument is everything after the space in the program path. What do I need to do to the exec command so that the only argument the called program sees is the one I explicitly passed it?

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Re: System, exec different behaviour with spaces
by Anonymous Monk on Jan 12, 2012 at 10:08 UTC

      Thanks for the pointers - I'm somewhat clearer about where the problem comes from, even if the fix is somewhat convoluted (I need to support multiple platforms). What I still don't get is why the behaviour is OK when using system, but not exec. I'd have thought that in terms of their argument passing the two would have been equivalent.

        What I still don't get is why the behaviour is OK when using system, but not exec.

        Perhaps you didn't notice, but that is what I asked :)

        Though, at this point, i don't really care what the answer is :)

Re: System, exec different behaviour with spaces
by ikegami (Pope) on Jan 13, 2012 at 07:09 UTC

    You can work around this weirdness by using the following:

    perl -e"$prog = 'C:\Program Files\Java\jdk1.6.0_15\bin\java.exe'; exec + { $prog } 'java', '-version'"

    It doesn't work if you use the full path after the curlies.

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