We are using a set of external binaries on Windows to, roughly speaking, control a job management system. For this discussion it is sufficient to know that there exists a bkill.exe, which can be used from the Windows command line to kill a job: 

bkill.exe 4711

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kills the job with number 4711. If this job has already terminated at the time of killing, we get not surprisingly the message 
Job <4711>: Job has already finished

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on standard error. Now comes the funny thing: When I call the program from Perl, say with 
perl -lwe  "system(qq(bkill 4711))"

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I get the following answer under ActiveState Perl 5.10: 
Job <4711>: Job has already finished
Can't spawn "bkill.exe 4711": No error at -e line 1.

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Even without knowing anything about the internals of bkill.exe, I wonder why this error is displayed (after all, it obviously *could* spawn bkill.exe), and why this is considered as "No error".

Since I also happen to have Perl 5.7 installed, I tried it with this version too, and here, the output looks even funnier: 

Job <4711>: Job has already finished
Job <4711>: Job has already finished
Can't spawn "cmd.exe": No such file or directory at -e line 1.

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This gives some hint: Maybe Perl 5.7 thought too that it could not spawn the process, but maybe - different to 5.10 - retries once until giving up.

The problem does not appear so far with any other program (and also with bkill only in this certain circumstance - for instance, "killing" a job which has never existed, or killing an existing job, does not show any unusual output). Now of course we have no oddities what is going on within bkill - I don't have the source code -, but no matter what it is, how could possibly be Perl tricked into thinking that it could not spawn the process?

-- 
Ronald Fischer <ynnor@mm.st>

In reply to What error is "No Error" by rovf

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