read-write troubles

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

I have some code that does somthing like this:

open FILE, "+<$filename";
undef $/;
$old_data = <FILE>;
#do some stuff
seek FILE, 0, 0;
print FILE $new_data;
[download]

This works fine, except when $new_data is smaller than $old_data. In that case, I get the end of $old_data left in my file, which isn't what I want. Is there a way I can either shrink the file to zero size instead of just seeking to the beginning, or tell perl to end the file at the current cursor position, ignoring everything after it? Or should I just give in and close the file and re-open it?

--
Ryan Koppenhaver, Aspiring Perl Hacker
"I ask for so little. Just fear me, love me, do as I say and I will be your slave."

Comment on read-write troubles Download Code

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(Ovid) Re: read-write troubles by Ovid (Cardinal) on Nov 03, 2000 at 21:55 UTC
`open FILE, "+<$filename" or die "I checked a return call: $!\n"; { local $/; # Always localize this so it doesn't interfere with othe +r parts of the program. $old_data = <FILE>; } #do some stuff seek FILE, 0, 0 or die "Can't seek on $filename: $!\n"; print FILE $new_data or die "Can't print to $filename: $!\n"; truncate FILE, tell(FILE) or die "Can't truncate $filename: $!\n"; close FILE or die "Can't close $filename: $!\n";` [download] Cheers, Ovid Join the Perlmonks Setiathome Group or just go the the link and check out our stats.	[reply] [d/l]
RE: read-write troubles by Albannach (Monsignor) on Nov 03, 2000 at 21:52 UTC
I think you're looking for truncate().	[reply]
RE: RE: read-write troubles by rlk (Pilgrim) on Nov 03, 2000 at 22:12 UTC
Yep, that's what I needed. Thanks. -- Ryan Koppenhaver, Aspiring Perl Hacker "I ask for so little. Just fear me, love me, do as I say and I will be your slave."	[reply]
RE (tilly) 3: read-write troubles by tilly (Archbishop) on Nov 03, 2000 at 23:11 UTC
And to forstall your next question, look at flock. :-)	[reply]