in reply to Returning a list from a sub

Hello

Almost nothing to add to VSarkiss's excellent answer : It would be more perlish to select inside the loop lines containing "3584". Indeed, using a double pipe, you create a extra process for the grep. This solution avoids it : 

open(IN,"adsm_cmd q libv|");
open(OUT,">/tmp/show_library.$$");

while (<IN>) {
  next unless (/3584/);
  
  # VSarkiss stuff
  ...
}

[download]

HTH

--
zejames

Replies are listed 'Best First'.
Re: Re: Returning a list from a sub
by coec (Chaplain) on Jul 24, 2002 at 04:16 UTC
    Thanks for the great advice.
    I'm still stuck, though, on how to loop through this list from the calling sub. 
    sub TSM_Enquire {
  my $Slot, $Type, $Label;

  open(IN,"/bbs/rtscripts/adsm_cmd q libv|");

  while (<IN>) {
    next unless (/3584/);
    s/,//;
    @Fields = split ' ';
    $Label = $Fields[2];
    $Slot = $Fields[$#Fields-1];
    $Type = $Fields[3];
    push @List, "$Slot $Type $Label";
  }

  close(IN);
  return @List;
}

sub Process_Columns {
  my $Count=0;
  my $Simple;
  my @Column_Info = ( [ 1024, 1067 ],     # Column 1 start stop
                      [ 1068, 1093 ],     # Column 2 start stop
                      [ 1094, 1137 ],     # Column 3 start stop
                      [ 1138, 1163 ],     # Column 4 start stop
                      [ 1164, 1207 ],     # Column 5 start stop
                      [ 1208, 1233 ],     # Column 6 start stop
                      [ 1234, 1277 ],     # Column 7 start stop
                      [ 1278, 1321 ] );   # Column 8 start stop

  if ($LibraryType =~ "tsm") {
     @List = TSM_Enquire;
  } else {
     @List = Tapeutil_Enquire;
  }

  for ($Count=1;$Count<=8;$Count++) { # Traverse columns
    my $StartPos = $Column_Info[$Count][1];
    my $Pos = $StartPos; 
    my $Column_Count = 0;
    my $EndPos = $Column_Info[$Count][2];
    my $NewPos=0;
    my $NewLabel="";
    my $NewRec="";

    while ($NewRec = @List) {
      chomp $NewRec;
      $NewRec =~ s/^ //;
      ($Pos, $Type, $Label) = split(' ', $NewRec, 9999);
      for ($I=1;$I<=($EndPos-$StartPos)+1;$I++) {
<snip>

    [download]
    I that the above is wrong (because it doesn't work, read as: doesn't do what I want).
    Any ideas, comments, etc?
    TIA
    coec
[reply]
[d/l]
      It looks suspiciously like you have a scoping issue with @List. What is probably happening is that you have (either explicitly or implicitly) created a *global* variable called @List, rather than a local variable within each subroutine. I would suggest adding my @List; to the beginning of your TSM_Enquire and Process_Columns subs, which will give them each a private copy of the list that is empty each time the sub is first executed. For more details, you can check out the sections on scoping in perldoc perlsub.

      Also, you might also want to use strict; at the beginning of your program to help catch errors like this in the future.

      If that doesn't solve the problem, it might be worth trying some simple debugging tricks, like adding warn statements on subroutine entry and exit and when you are manipulating @List or other variables that are central to what your code is trying to accomplish.

[reply]

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