Re^4: Empty File Contents before writing

There is also a built-in function called truncate that will do what you want.

$ perl -Mstrict -Mwarnings -e '
> open my $fh, q{>}, q{rubbish} or die $!;
> print $fh qq{A longish line of text\n};
> truncate $fh, 0 or die $!;
> print $fh qq{Short\n};
> close $fh  or die $!;'
$ cat rubbish
Short
$
[download]

Update: Added example code.

Cheers,

JohnGG

Comment on Re^4: Empty File Contents before writing Download Code

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Re^5: Empty File Contents before writing by RichardK (Parson) on Feb 19, 2013 at 11:41 UTC
The help for truncate says `The position in the file of FILEHANDLE is left unchanged. You may want + to call seek before writing to the file.` [download] So, any ideas why your code works without needing a seek 0?	[reply] [d/l]
Re^6: Empty File Contents before writing by johngg (Canon) on Feb 19, 2013 at 14:37 UTC
You are right. I hadn't read the documentation carefully enough and hadn't spotted that. Running `hexdump -C` shows that a seek is indeed necessary. `$ perl -Mstrict -Mwarnings -e ' > open my $fh, q{>}, q{rubbish} or die $!; > print $fh qq{A longish line of text\n}; > truncate $fh, 0 or die $!; > print $fh qq{Short\n}; > close $fh or die $!;' $ cat rubbish Short $ hexdump -C rubbish 00000000 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 \|......... +.......\| 00000010 00 00 00 00 00 00 00 53 68 6f 72 74 0a \|.......Sh +ort.\| 0000001d $` [download] Thank you for the correction. Cheers, JohnGG	[reply] [d/l] [select]