It's fairly simple to demonstrate that this is not true...

jasonk@critter% cat foo.pl

#!/usr/bin/perl -w
##################
open(OUT,">/tmp/testfileA");
print OUT "This is testfileA\n";
close(OUT);

open(OUT,">/tmp/testfileB");
print OUT "This is testfileB\n";
close(OUT);

open(IN,"/tmp/testfileA");
system("mv /tmp/testfileB /tmp/testfileA");

print <IN>;                                                           
+          

jasonk@critter% ./foo.pl

This is testfileA
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Ok, I stand corrected. I have no access to a box to test with, so I was guessing.

I suppose that the rename is just changing the directory entry. I believe that a /bin/cp will give the exact semantics that I supposed earlier? Maybe someone will check for me.

Or maybe I'll just get downvoted.

,welchavw

Well, he meant "rename" when he said "rename"?! (it's linked to perl rename)

-> Code should look like this


$ cat foo.pl 
#!/usr/bin/perl -w
##################
open(OUT,">testfileA");
print OUT "This is testfileA\n";
close(OUT);

open(OUT,">testfileB");
print OUT "This is testfileB\n";
close(OUT);

open(IN,"/tmp/testfileA");

rename ("testfileB", "testfileA");

print <IN>;
close IN;
[download]


Yields:

$ ./foo.pl 
readline() on closed filehandle IN at ./foo.pl line 15.
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So the answer is "neither - rename closes the filehandle". I.

So the answer is "neither - rename closes the filehandle".

I think you missed the bit about "... two concurrent (Perl) processes ..." and "... when the second process next reads via it's open handle ..."

A better test would be

#!/usr/bin/perl
use strict;
use warnings;

open OUT, '>', 'junk.1' or die $!;
print OUT 'X'x 20 . "$_\n" for 1 .. 20;
close OUT;

open OUT, '>', 'junk.2' or die $!;
print OUT 'Y'x 20 . "$_\n" for 1 .. 20;
close OUT;

open IO, '+<', 'junk.1' or die $!;
seek IO, 0, 0;
print scalar <IO>;

system $^X, '-le', q[ print rename( 'junk.2', 'junk.1' ) ? 'worked' : 
+'failed'];

print scalar <IO>;

seek IO, 0, 0;

print scalar <IO>;

close IO;

unlink 'junk.1';
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---

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Lingua non convalesco, consenesco et abolesco. -- Rule 1 has a caveat! -- Who broke the cabal?

"Science is about questioning the status quo. Questioning authority".

In the absence of evidence, opinion is indistinguishable from prejudice.