New Line removal from both Unix & Win32

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

Hello monks,

I've been using the following code thanks to jmcnamara

 if ($^O eq 'MSWin32') {
    open my $fh, "+<$Conf[1]" or warn "$!";
    binmode $fh;

    my $size = 4096;

    seek $fh, -$size, 2;
    # Locate the end of the file
    while (1) {
    $cur_pos = tell $fh;
    read $fh, $buf, $size;
    last if $buf =~ m/\S/s;
    seek $fh, -$size*2, 1;
    }

    $buf =~ m/(\s*)$/s;
    $cur_pos += $-[0] || 0;

    truncate $fh, ++$cur_pos if $cur_pos;

    close $fh;
    }
[download]

I had to check for the OS because this routine fails on Unix, does anyone know why?

Thanks

Comment on New Line removal from both Unix & Win32 Download Code

Replies are listed 'Best First'.
Re: New Line removal from both Unix & Win32 by Aristotle (Chancellor) on Dec 30, 2002 at 17:07 UTC
Please, never never use `$^O eq $foo`. Do a pattern match instead: `$^O =~ /Win32/i`. But judging from your error message I'm guessing that your Linux box is using an older version of Perl (5.005 or earlier) which doesn't autovivify filehandles so it's barfing at the open with a lexical variable. You have to write it as follows: `use Symbol (); my $fh = Symbol::gensym(); open $fh, "+<", $Conf[1] or warn "$!";` [download] And please please use the three-argument from of open (as shown in my snippet). Makeshifts last the longest.	[reply] [d/l]
Re: New Line removal from both Unix & Win32 by Zaxo (Archbishop) on Dec 30, 2002 at 16:20 UTC
What error message do you get on Unix? I don't see any obviously wrong operations. Is `$Conf[1]` a file name in non-portable winders-like form? If that's all, Perl can assist in producing more portable file name code. See perlport. After Compline, Zaxo	[reply]
Re: New Line removal from both Unix & Win32 by waswas-fng (Curate) on Dec 30, 2002 at 18:17 UTC
One more question, why `open my $fh, "+<$Conf[1]" or warn "$!";` not `open my $fh, "+<$Conf[1]" or die "$!";` as from the snippet you have there you have no work around for failed open -- it can't handle it so it may as well die and be safe. -Waswas	[reply] [d/l] [select]
Re: Re: New Line removal from both Unix & Win32 by Anonymous Monk on Dec 30, 2002 at 19:15 UTC
The code below is no longer getting an error but is failing to remove new lines from the end of files in the Unix environment `my $fh = Symbol::gensym(); open $fh, '+<$Conf[1]' or warn "$!"; binmode $fh; my $size = 4096; seek $fh, -$size, 2; # Locate the end of the file while (1) { $cur_pos = tell $fh; read $fh, $buf, $size; last if $buf =~ m/\S/s; seek $fh, -$size2, 1; } $buf =~ m/(\s)$/s; $cur_pos += $-[0] \|\| 0; truncate $fh, ++$cur_pos if $cur_pos; close $fh;` [download] Any ideas why Thanks again	[reply] [d/l]
Re: New Line removal from both Unix & Win32 by Nitrox (Chaplain) on Dec 30, 2002 at 16:16 UTC
Without being provided any error messages I can only speculate that Unix file permissions may be coming into play. -Nitrox	[reply]
Re: Re: New Line removal from both Unix & Win32 by Anonymous Monk on Dec 30, 2002 at 16:22 UTC
Sorry, The error is: `Can't use an undefined value as a symbol reference at test.pl.` [download]	[reply] [d/l]


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