PerlIO omission

[Bo Lindbergh]

Why is there no truncate operation in PerlIO?

/Bo Lindbergh

 

[Ben Morrow]

Why is there no truncate operation in PerlIO?

Err...cos PerlIO's broken?
There seems to be some sort of abstraction of the operation, but systems
with ftruncate(2) always end up calling it on fileno($FH).

Ben

 

[Charles DeRykus]

Why is there no truncate operation in PerlIO?

There is though: perldoc -f truncate

 

[Charles DeRykus]

There is though: perldoc -f truncate

I think there is an emulation even on OS's
which don't have ftruncate(2).

On Win32 for instance, truncate still succeeds:

C:\temp>perl -V:d_truncate
d_truncate='undef';

C:\temp>perl
open my $fh, "+<", "foo" or die "open: $!";
truncate $fh,0 or die "truncate failed";
^D

 

[Bo Lindbergh]

There is though: perldoc -f truncate

"PerlIO", not "Perl I/O". There's a difference.


/Bo Lindbergh

 

[Bo Lindbergh]

Err...cos PerlIO's broken?
There seems to be some sort of abstraction of the operation, but systems
with ftruncate(2) always end up calling it on fileno($FH).

And so truncate fails with EBADF in the example below.

{
open(my $fh,">",\my $buffer)
or die "open: $!";
print $fh "Hello, World!\n"
or die "print: $!";
truncate($fh,5)
or die "truncate: $!";
}

This is sad, because truncating a Perl scalar is a perfectly
reasonable thing to want to do.


/Bo Lindbergh

 

[Charles DeRykus]

"PerlIO", not "Perl I/O". There's a difference.

Oops, yes. That's "big boy" stuff...