Re: @ARGV while (<>) hangs

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sub delimit {
    my ( $tos, $ccs, $rp, $sb, $body, $in_file ) = @_;
    my @lines;
    if ( defined $in_file ) {    # file submited
        @ARGV = $in_file;
        $body = "";
        while (<>) {
            push( @lines, $_ ) unless (/espf\[/);    # hangs here some
+times
        }    # end of while
    }    # end of if
}    # end of sub
[download]

If you wrote the "delimit" sub, perhaps you could describe in words what you are trying to accomplish. It seems like you are trying to open a file named by the $in_file variable. Perhaps if you use the open function, instead of assigning to @ARGV (which is a little unusual), you could at least get some information as whether the input file exists. For example:

open my $fh, '<', $in_file or die "Error: can not open file $in_file $
+!";
[download]

Comment on Re: @ARGV while (<>) hangs Select or Download Code

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Re^2: @ARGV while (<>) hangs by ikegami (Patriarch) on Jan 08, 2008 at 23:00 UTC
It's a really bad idea to modify globals (`@ARGV` and `$_` in this case) without localizing them. `local @ARGV = ...; local $_; while (<>) { ... }` [download]	[reply] [d/l] [select]
Re^2: @ARGV while (<>) hangs by gatorreina (Initiate) on Jan 08, 2008 at 21:31 UTC
The delimit sub is designed to check and see if an infile is submitted and if it is remove any line from the $in_file that contains the characters espf[. The @ARGV while (<>) schema is because I got it from page 72 of my Learning Perl (4th addition) book.	[reply]
Re^3: @ARGV while (<>) hangs by WoodyWeaver (Monk) on Jan 08, 2008 at 23:04 UTC
I think you are not well served by page 72 of Learning Perl. It is far more clear, and much easier to debug, if you open the file directly, after checking, than in the background. If you are feeling daring, then go with toolic's `open F, '<', $in_file or die "Can't open $in_file: $!";` [download] followed by `while (<F>) { push @lines, $_ unless /espf\[/ }` [download] although if the goal is to edit $in_file deleting lines, then you probably don't want to push it into a temporary array, but instead open a temp file, write to the temp file, unlink $in_file, and rename the temp file to $in_file. However, since this is probably doing a ton of disk access, I'd probably do a few sanity checks first. `return undef if not defined $in_file; if (-e $in_file) { if (-r $in_file) { open F, "<", $in_file or die "Can't open $in_file: $!" # etc } else { warn "can't read $in_file\n"; return undef; } } else { warn "bad file $in_file submitted, but does not exist\n"; }` [download] Part of the reason I say that reassigning ARGV is not good practice is the principle of least surprise. The "while (<>)" construct is best used in the fashion described in perlopentut: One of the most common uses for open is one you never even notice. When you process the ARGV filehandle using <ARGV>, Perl actually does an implicit open on each file in @ARGV. Thus a program called like this: `$ myprogram file1 file2 file3` [download] Can have all its files opened and processed one at a time using a construct no more complex than: `while (<>) { # do something with $_ }` [download] If @ARGV is empty when the loop first begins, Perl pretends you've opened up minus, that is, the standard input. In fact, $ARGV, the currently open file during <ARGV> processing, is even set to "-" in these circumstances. While you can use the magic of an implicit open to open files, its better to avoid magic when possible for the next poor sap who has to debug your code. --woody	[reply] [d/l] [select]