Re^5: Empty File Contents before writing

in reply to Re^4: Empty File Contents before writing
in thread Empty File Contnts before writing

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?

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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]

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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

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