#!/usr/bin/env bash

# @(#) s2	Demonstrate differences at character level.

pe() { for _i;do printf "%s" "$_i";done; printf "\n"; }
pl() { pe;pe "-----" ;pe "$*"; }
db() { ( printf " db, ";for _i;do printf "%s" "$_i";done;printf "\n" ) >&2 ; }
db() { : ; }
C=$HOME/bin/context && [ -f $C ] && $C perl docdiff 

f1=data1
f2=data2
FILES="$f1 $f2"

pl " Input files $FILES"
head $FILES

pl " perl extraction helper script:"
cat p1

pl " Results, wdiff format, $f1, $f2:"
docdiff --wdiff --char $f1 $f2

pl " Results, wdiff format, $f1, $f2, extracted diff with labels:"
docdiff --wdiff --char $f1 $f2 |
./p1 $f1 $f2

pl " Results, wdiff format, $f2, $f1, extracted diff with labels:"
docdiff --wdiff --char $f2 $f1 |
./p1 $f2 $f1

exit 0

% ./s2

Environment: LC_ALL = C, LANG = C
(Versions displayed with local utility "version")
OS, ker|rel, machine: Linux, 2.6.26-2-amd64, x86_64
Distribution        : Debian GNU/Linux 5.0.8 (lenny) 
bash GNU bash 3.2.39
perl 5.10.0
docdiff 0.3.4

-----
 Input files data1 data2
==> data1 <==
orange
123456789xa
X-klystron

==> data2 <==
orange
123456780xb
Y-klystron

-----
 perl extraction helper script:
#!/usr/bin/env perl

# @(#) p1	Demonstrate wdiff difference format extraction with labels.

$f1 = shift || die " Missing first label.\n";
$f2 = shift || die " Missing second label.\n";

while (<>) {
  @a = m/\[-(.*?)-\]/xmsg;
  print "$f1: ", join( "", @a ), "\n" if defined @a;
  @b = m/\{\+(.*?)\+\}/xmsg;
  print "$f2: ", join( "", @b ), "\n" if defined @b;
}

exit(0);

-----
 Results, wdiff format, data1, data2:
orange
12345678[-9-]{+0+}x[-a-]{+b+}
[-X-]{+Y+}-klystron

-----
 Results, wdiff format, data1, data2, extracted diff with labels:
data1: 9a
data2: 0b
data1: X
data2: Y

-----
 Results, wdiff format, data2, data1, extracted diff with labels:
data2: 0b
data1: 9a
data2: Y
data1: X

#!/usr/bin/env perl

# @(#) p1	Demonstrate character differences in same-length lines.

use warnings;
use strict;

my (
  $f1, $f2, $file1, $file2, $i,       @a, @b,
  $s1, $s2, $t1,    $t2,    $changed, $debug
);

$f1 = shift || die " Missing first file.\n";
$f2 = shift || die " Missing second file.\n";

$debug = 1;
$debug = 0;

open( $file1, "<", $f1 ) || die " Cannot open file $f1\n";
open( $file2, "<", $f2 ) || die " Cannot open file $f2\n";
while ( $t1 = <$file1> ) {
  chomp($t1);
  @a = split "", $t1;
  $t2 = <$file2>;
  chomp($t2);
  @b = split "", $t2;
  print "file1,2 = ", join "", @a, " ", join "", @b, "\n" if $debug;
  $changed = 0;
  $s1 = $s2 = "";

  for ( $i = 0; $i <= $#a; $i++ ) {
    if ( $a[$i] ne $b[$i] ) {
      $s1 = "$f1: " if not $changed;
      $s2 = "$f2: " if not $changed;
      $s1 .= $a[$i];
      $s2 .= $b[$i];
      $changed++;
    }
  }
  print "$s1\n" if $changed;
  print "$s2\n" if $changed;
}

exit(0);

% ./p2 data1 data2
data1: 9a
data2: 0b
data1: X
data2: Y