On Fri, 2009-03-20 at 11:07 -0700, John W. Krahn wrote:
> Martin Spinassi wrote:
> > Hi list!
>
> Hello,
>
> > I've just started with perl, but I'm really excited about its power.
>
> I'm excited that you're excited! ;-)
I'm excited because you are excited because I'm....or....you.....
doesn't mind :-D
[snip]
> > Is there any way to open a file for input and output at the same time?
>
> perldoc -f open
>
> [ snip ]
>
> You can put a '+' in front of the '>' or '<' to indicate that
> you want both read and write access to the file; thus '+<' is
> almost always preferred for read/write updates--the '+>' mode
> would clobber the file first. You can’t usually use either
> read-write mode for updating textfiles, since they have variable
> length records. See the -i switch in perlrun for a better
> approach. The file is created with permissions of 0666 modified
> by the process’ "umask" value.
>
>
> > This is just and example, and doesn't work, but may be it explains
> > better what I'm trying to do:
> >
> >
> > while (glob "*.dump") { #I know there is not a "<>"
> > open (TMPFILE,"<&>", $_) or die "Could not open file $_: $!\n";
> >
> > while (<TMPFILE>) {
> > s/^--.*//;
> > print;
> > }
> > }
>
> Your best bet is probably to read the entire file into memory, modify
> it, and then write it back out. Something like this (UNTESTED):
>
> use Fcntl ':seek';
>
> while ( my $file = glob '*.dump' ) {
> open my $TMPFILE, '+<', $file or die "Could not open file $file: $!\n";
> local $/;
> my $data = <$TMPFILE>;
> $data =~ s/^--.*//gm;
> seek $TMPFILE, 0, SEEK_SET or die "Could not seek file $file: $!\n";
> print $TMPFILE $data;
> truncate $TMPFILE, length $data;
> }
>
>
> Other methods would include using Tie::File or one of the mmap modules.
> For example:
>
> use Tie::File;
>
> while ( my $file = glob '*.dump' ) {
> tie my @data, 'Tie::File', $file or die "Could not open file $file:
> $!\n";
> s/^--.*// for @data;
> untie @data;
> }
>
>
>
>
> John
> --
> Those people who think they know everything are a great
> annoyance to those of us who do. -- Isaac Asimov
>
Wow! those looks pretty complicated (to me, of course, and anything
beyond "Hello world" is by now). You just make me curious about "untie",
"Fcntl ':seek'", "seek", and "truncate". I'll test them (and probably
back here) and tell you how is it going! ;-)
Thanks John
Cheers
Martín
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