Reading chunks of text

Hue-Bond has asked for the wisdom of the Perl Monks concerning the following question:

I'm about to parse the output of xlsclients -la. It's like this:

Window 0x800022:
  Machine:  genus
  Name:  xterm
  Icon Name:  xterm
  Command:  xterm -u8 -geometry 156x62+190+-2
  Instance/Class:  xterm/XTerm
Window 0xc00022:
  Machine:  genus
  Name:  ~
  Icon Name:  psh
  Command:  xterm -e /usr/bin/psh
  Instance/Class:  xterm/XTerm
Window 0xe00001:
  Machine:  genus
  Name:  Gecko
  Icon Name:  mozilla-bin
  Command:  mozilla-bin
  Instance/Class:  mozilla-bin/Mozilla-bin
[download]

There's no blank link between "paragraphs" so I can't use $/ = "\n\n". I want to do something simple that gives me whole paragraphs without eating anything (so $/ = "\nWindow" wouldn't fit). I'm thinking about reading six lines at a time but I find it ugly:

open my $fd, 'xlsclients -la|' or die "open: $!";
WHILE: while (1) {
  my @para;
  foreach (1..6) {
    my $line = <$fd>;
    defined $line or last WHILE;
    push @para, $line;
  }
  print "@para\n";   ## quotes intended in this small example
}
close $fd;
[download]

Is there anything more I can do?

--
David Serrano

Comment on Reading chunks of text Select or Download Code

Replies are listed 'Best First'.
Re: Reading chunks of text by holli (Abbot) on Aug 21, 2006 at 08:06 UTC
You can use the fact that all lines of the paragraphs are indented, but the first line. `my @p; while (<DATA>) { push @p, [], if /^Window/; push @{$p[-1]}, $_; }` [download] or maybe you want a hash and use the window handles as keys: `my %h; while (<DATA>) { $key = $1, next if /^Window ([^:]+)/; push @{$h{$key}}, $_; }` [download] holli, /regexed monk/	[reply] [d/l] [select]
Re: Reading chunks of text by cog (Parson) on Aug 21, 2006 at 08:06 UTC
Is there anything more I can do? Yes, there is. `while (my @a = grep defined, map scalar <$fd>, 1 .. 6) { # do whatever you want with @a, which has 6 lines }` [download] I asked a similar question, two years ago.	[reply] [d/l]
Re: Reading chunks of text by shmem (Chancellor) on Aug 21, 2006 at 08:12 UTC
Maybe this? (untested) `while(my $line = <$fd>) { $line =~ /^Window/ ? push (@para, $line) : ($para[$#para] .= $line); }` [download] --shmem _($_=" "x(1<<5)."?\n".q·/)Oo. G°\ / /\_¯/(q / ---------------------------- \__(m.====·.(_("always off the crowd"))."· ");sub _{s./.($e="'Itrs `mnsgdq Gdbj O`qkdq")=~y/"-y/#-z/;$e.e && print}	[reply] [d/l]
Re: Reading chunks of text by Fletch (Bishop) on Aug 21, 2006 at 12:58 UTC
Actually that's coincidentally valid YAML: `$ xlsclients -la \| perl -MYAML -MData::Dumper -le '$x = do { local $/; + <>}; print Data::Dumper::Dumper( YAML::Load( $x ) )' $VAR1 = { 'Window 0x600001' => { 'Command' => 'xemacs', 'Machine' => 'foo', 'Icon Name' => 'xemacs', 'Instance/Class' => 'xemacs/Emacs', 'Name' => 'xemacs' }, 'Window 0xa0000e' => { 'Command' => 'xterm -display :11 -geo +m +0-25', 'Machine' => 'bar.phydeaux.org', 'Icon Name' => 'fletch@bar:~', 'Instance/Class' => 'xterm/XTerm', 'Name' => 'fletch@bar:~' } };` [download]	[reply] [d/l]
Re: Reading chunks of text by GrandFather (Saint) on Aug 21, 2006 at 11:23 UTC
An interesting but fragile technique is to alter the input record seperator $/: use strict; use warnings; local $/ = "Window "; while (<DATA>) { chomp; next if ! length; my $paragraph = $/ . $_; print "$paragraph\n"; } __DATA__ Window 0x800022: Machine: genus Name: xterm Icon Name: xterm Command: xterm -u8 -geometry 156x62+190+-2 Instance/Class: xterm/XTerm Window 0xc00022: Machine: genus Name: ~ Icon Name: psh Command: xterm -e /usr/bin/psh Instance/Class: xterm/XTerm Window 0xe00001: Machine: genus Name: Gecko Icon Name: mozilla-bin Command: mozilla-bin Instance/Class: mozilla-bin/Mozilla-bin [download] Prints: `Window 0x800022: Machine: genus Name: xterm Icon Name: xterm Command: xterm -u8 -geometry 156x62+190+-2 Instance/Class: xterm/XTerm Window 0xc00022: Machine: genus Name: ~ Icon Name: psh Command: xterm -e /usr/bin/psh Instance/Class: xterm/XTerm Window 0xe00001: Machine: genus Name: Gecko Icon Name: mozilla-bin Command: mozilla-bin Instance/Class: mozilla-bin/Mozilla-bin` [download] DWIM is Perl's answer to Gödel	[reply] [d/l] [select]