Another possibility: If another job has the file open, then the delete won't work. In my environment (running cygwin under Windows XP), I see this all the time. IIRC, cygwin has a background thread, so if you remove the file, it will actually be deleted after the other processes release the file.

As an illustration, create a simple text file called zanzibar.txt, and run the following program in a window.

#!/usr/bin/perl
open INF, '<', 'zanzibar.txt' or die $!;
sleep 300;
close INF or die $!;
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Then, in another window, delete the file. On my system, I see this:

roboticus@swill$ ls
zanzibar.txt

roboticus@swill$ rm zanzibar.txt
roboticus@swill$ ls
zanzibar.txt
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If I wait five minutes and look again, it's gone:

roboticus@swill$ ls

roboticus@swill$
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