perl open mode

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

Evening,

I was fiddling about with the open mode '+<'.

open (A, '+<', "somefile.html") or die $!;
print A map{s/a/b/g;$_} <A>;
[download]

I know this is a bit of a mash up. But why is it that the files come out appended to as opposed to just over written. From what this feels like perl is acting like i called a '+>>'. Perl 5.8.8

Thanks

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Re: perl open mode by Sidhekin (Priest) on Oct 24, 2007 at 00:22 UTC
As you are reading from the file handle in list context, you advance its position until eof. Then you print. At the former eof. (If you had opened with `+>>`, you would not have been able to read anything without seeking first.) Update: For what you want, and with a tiny bit more clarity: `open (A, '+<', "somefile.html") or die $!; s/a/b/g for my @records = <A>; seek(A, 0, 0); print A @records;` [download] `print "Just another Perl ${\(trickster and hacker)},"` The Sidhekin proves Sidhe did it!	[reply] [d/l] [select]
Re^2: perl open mode by snopal (Pilgrim) on Oct 24, 2007 at 03:16 UTC
That works if the replacement is character for character. You may be surprised by the results if the replacements are shorter than the original value. `open (A, '+<', "somefile.html") or die $!; s/a/b/g for my @records = <A>; seek(A, 0, 0); ### truncate (A, 0) or die "can not truncate file to zero length\n"; ### print A @records;` [download]	[reply] [d/l]


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