Ding!
Many thanks James. I was so fixated on the second loop I failed to
see that the undef really occurred in the return to the first.
Unfortunately, I think I need to retain the second loop. I need to
process the file $schemafile one line at a time, as every line of that file
contains exactly one XML tag. Most of the "work" in the script is actually
accomplished by the statement $newelement =~ s/>a/>$data[$count]/; --
within that second loop.
Is there any was I can set a marker for $_ in the original while
loop to avoid the undef and return to process the next line? Or am I stuck
with slurping the first file into an array in its entirety and processing
only the second file with a loop?
Thanks for your help,
Rob
-----Original Message-----
From: James Edward Gray II [mailto:[EMAIL PROTECTED]]
Sent: Thursday, October 10, 2002 2:33 PM
To: Diethorn, Robert - MBDC
Cc: '[EMAIL PROTECTED]'
Subject: Re: Newbie - reading from files in nested while loops
On Thursday, October 10, 2002, at 01:12 PM, Diethorn, Robert - MBDC
wrote:
[snip]
>
> #!/usr/bin/perl
> use strict;
> use warnings;
>
>
> my $datafile = $ARGV[0]; # read 1st argument into
> variable $datafile
> my $schemafile = $ARGV[1]; # etc.
> my $outputfile = $ARGV[2]; # etc.
>
> open (DATAIN,"$datafile"); # open file named by $datafile for
> reading
Be sure and check that an open call succeeds, returns a true value.
Typical Perl opens have the form:
open DATAIN, "$datafile" or die "Error opening file: $!\n";
> open (SCHEMAIN,"$schemafile"); # open file named by
$schemafile for
> reading
> open (XMLOUT, ">>$outputfile"); # open file named by
$outputfile for
> writing (appending)
Ditto for these two.
> print XMLOUT "<substance>\n"; # print opening substance tag to
> outputfile
>
> while (<DATAIN>) {
> chomp;
> my @data = split (/~/,$_); # read line from file called
> by DATAIN into array @data; assign elements split by "~" character
>
> my $count = 0;
> while (<SCHEMAIN>) { # read one line of
> schemafile to $_ while lines are available to read
I think the above line is your main problem. You're reading in one
line of DATAIN, then reading all of SCHEMAIN, an then going back for
line two of DATAIN. When you get back here, you're reading from an
exhausted filehandle, which returns undef and is likely what's
triggering the warning. How about combine this with a couple of lines
below and do:
chomp(my $newelement = <SCHEMAIN>);
> my $length = @data; # assign the number
> of array elements to variable $length
> my $newelement = $_; # assign the current
> line of input from schemafile to variable $newelement
No longer needed.
> $newelement =~ s/>a/>$data[$count]/; # search for ">a" in
> current line; replace with ">" and a single element from the array
> @data
> chomp ($newelement);
Ditto. Not needed.
> print XMLOUT "$newelement\n"; # write new line of
> text to outputfile
> $count++; # increment variable
> $count
> }
> }
>
> print XMLOUT "</substance>\n"; # print closing substance
tag and
> newline to outputfile
>
> close (XMLOUT);
> close (SCHEMAIN);
> close (DATAIN);
>
> print "datafile = $datafile and schemafile = $schemafile and
> outputfile =
> $outputfile";
Well, that's what jumps out at me on the first scan. See if that helps
you along and if it doesn't send it back for round two. Good luck!
James Gray
>
> ____________
> Rob Diethorn
> Systems Administrator
> McDonough Braungart Design Chemistry, LLC
>
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