Isaac Clarke Isaac Clarke - 6 days ago 5
Perl Question

Can I read and write to multiple filehandles simultaneously (Perl)?

I'm trying to read from two files, and generate output in a third. I first wanted to edit the first one on the go but I didn't find a suitable method save for arrays.

My problem is that the third file (output) is empty whenever I uncomment the "_ref_param_handling" function. BUT the following is what puzzles me the most: If I do a UNIX very basic `cat` system call on the output file at then end (see code below), it works just fine. If I open the filehandle just before and close it right after editing, it also works fine (around my print FILEHANDLE LIST).

I undoubtedly am missing something here. Apart from a problem between my keyboard and my chair, what is it? A filehandle conflict? A scope problem?

Every variable is declared and has the value I want it to have.

Edit (not applicable anymore).
Using IO::File on the three files didn't change anything.

Edit 2 : New full subroutine code

My code works (except when my ref already exists, but that's because of the "append" mode i think) but there might be some mistakes and unperlish ways of coding (sorry, Monks). I, however, use Strict and warnings !

sub _ref_edit($) {
my $manda_def = "$dir/manda_def.list";
my $newrefhandle;
my $ref = $_[0];
(my $refout = $ref) =~ s/empty//;
my $refhandle;
my $parname = '';
my $parvalue = '';
my @val;


my $flush = readline STDIN; # Wait for <enter>

# If one or both of the ref. and the default values are missing
if ( !( -e $manda_def && -e $ref ) ) {
die "Cannot find $ref and/or $manda_def";

# Open needed files (ref & default)
open( $refhandle, "<", $ref ) or die "Cannot open ref $ref : $!";
open( $newrefhandle, ">>", $refout )
or die "Cannot open new ref $refout : $!";

# Read each line
while ( my $refline = <$refhandle> ) {
# If line read not an editable macro
if ( $refline =~ /^define\({{(.+)}},\s+{{.*__VALUE__.*}}\)/ ){
$parname = $1; # $1 = parameter name captured in regexp
# Prompt user
$parvalue = _ref_param_handling( $parname, $manda_def );
# Substitution in ref
$refline =~ s/__VALUE__/$parvalue/;
# Param not specified and no default value
$parvalue eq '' ? $refline=~s/__COM__/#/ : $refline=~s/__COM__//;

print $newrefhandle $refline;
close $newrefhandle;
close $refhandle;

return $refout;
} # End ref edit

the _ref_param_handle subroutine still is :

open( $mde, '<', $_[1] )
or die "Cannot open mandatory/default list $_[1] : $!";

# Read default/mandatory file list
while (<$mde>) {
( $name, $manda, $default, $match, $descript ) = split( /\s+/, $_, 5 );
next if ( $name !~ $ref_param ); # If param read differs from parname


} # End while <MDE>
close $mde;
return $input;

Extract from manda_def file :

NAME Mandatory? Default Match Comm.
PORT y NULL ^\d+$ Database port
PROJECT y NULL \w{1,5} Project name
SERVER y NULL \w+ Server name
modemRouting n NULL .+
modlib y bin .+
modules y sms .+

Extract from ref_file :

define({{PORT}}, {{__VALUE__}})dnl
define({{PROJECT}}, {{__VALUE__}})dnl
define({{SERVER}}, {{__VALUE__}})dnl
define({{modemRouting}}, {{__COM__{{$0}} '__VALUE__'}})dnl
define({{modlib}}, {{__COM__{{$0}} '__VALUE__'}})dnl
define({{modules}}, {{__COM__{{$0}} '__VALUE__'}})dnl

Any help appreciated.


Guys, I seriously consider hanging myself with my wireless mouse.

My script never failed. I just didn't ran it through the end (it's actually a very long parameter list). The printing is just done as soon as the filehandle is closed (or so I guessed)...

/me *cries*

I've spent 24 hours on this...