File::Copy move $! is "no such file" even on success

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

I'm trying to File::Copy::move a glob of files
I tried testing for $! and get a failure message for each file when it actually succeeded!
What am i missing??

Here's a code snippet (assume the glob array is ok)
(perl 5.6.1/linux)

# ------------------------
foreach my $f (@myGlob) {
   $!='';  # STILL complaining
   if (-l $f) { next; }
    move ($f,$RecBak) if (-f $f); 
   # failed to skip symbolic links 
   # till I said if -l $f next (why!?)
   if ($!) { print "\$!:[$!] $f FAILED! }
   else { print "$f moved" ;}
}
# ----------------------
[download]

This succeeds in moving all and only regular files as intended, but claims to fail!!
$! is always "no such file or directory".
I'm stuck..

thanks in advance,

- manchot

Comment on File::Copy move $! is "no such file" even on success Download Code

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Re: File::Copy move $! is "no such file" even on success by Abigail-II (Bishop) on Sep 12, 2003 at 15:03 UTC
$! is only set to a useful value if the function that you call fails. If it succeeds, you cannot draw conclusions from the value of $!. If you look at the source code of File::Copy, you see that the move command first tries a rename(). If that fails, it tries copying and unlinking. But if the rename() fails, rename() sets $! Even if the copy and unlink() succeeds. The right way to test whether move() succeeds is by checking its return value. Abigail	[reply]
Re: File::Copy move $! is "no such file" even on success by jeffa (Bishop) on Sep 12, 2003 at 15:07 UTC
How about something like this instead: `for my $f (@myGlob) { next unless -f $f; warn "can't move $f\n" unless move ($f,$RecBak); }` [download] jeffa L-LL-L--L-LL-L--L-LL-L-- -R--R-RR-R--R-RR-R--R-RR B--B--B--B--B--B--B--B-- H---H---H---H---H---H--- (the triplet paradiddle with high-hat)	[reply] [d/l]
Re: File::Copy move $! is "no such file" even on success by hardburn (Abbot) on Sep 12, 2003 at 14:56 UTC
~~`$!` isn't guarenteed to be reset after a successful call. I suspect you're seeing an error message from a previous call.~~ Update: Ignore the above. I didn't read the code closely enough. ---- I wanted to explore how Perl's closures can be manipulated, and ended up creating an object system by accident. -- Schemer Note: All code is untested, unless otherwise stated	[reply] [d/l]
Re: File::Copy move $! is "no such file" even on success by Abigail-II (Bishop) on Sep 12, 2003 at 15:08 UTC
$! isn't guarenteed to be reset after a successful call. I suspect you're seeing an error message from a previous call. If you look at the code, you see that $! is set before the call to move (it would generate a warning if they are turned on, but $! is still set to 0). $! will be set by move() (or by one of the function that it calls). You just shouldn't draw conclusions from it. Abigail	[reply]
Re: File::Copy move $! is "no such file" even on success by Anonymous Monk on Sep 12, 2003 at 15:15 UTC
Thanks a bunch, folks! I can hardly believe the instant high quality answers here! WOW! Thanks especially to Abigail-II for the full explanations, and to jeffa for the elegant alternative ;) manchot	[reply]
Re: File::Copy move $! is "no such file" even on success by Anonymous Monk on Sep 12, 2003 at 15:07 UTC
even tho I'm explicitly setting $!='' on each iteration?	[reply]
2Re: File::Copy move $! is "no such file" even on success by jeffa (Bishop) on Sep 12, 2003 at 15:21 UTC
You are explicitly setting `$!` before you call `File::Copy::move()`, so you only blow away the previous error. Also, 'blanking out' `$!` is kind of like removing the batteries from your smoke alarm - you are only going to regret it in the end. Happy coding, jeffa	[reply]