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      1 #! /usr/bin/perl -w
      2 
      3 # Script to take the output of nroff -man and remove all the backspacing and
      4 # the page footers and the screen commands etc so that it is more usefully
      5 # readable online. In fact, in the latest nroff, intermediate footers don't
      6 # seem to be generated any more.
      7 
      8 $blankcount = 0;
      9 $lastwascut = 0;
     10 $firstheader = 1;
     11 
     12 # Input on STDIN; output to STDOUT.
     13 
     14 while (<STDIN>)
     15   {
     16   s/\x1b\[\d+m//g;   # Remove screen controls "ESC [ number m"
     17   s/.\x8//g;         # Remove "char, backspace"
     18 
     19   # Handle header lines. Retain only the first one we encounter, but remove
     20   # the blank line that follows. Any others (e.g. at end of document) and the
     21   # following blank line are dropped.
     22 
     23   if (/^PCRE(\w*)\(([13])\)\s+PCRE\1\(\2\)$/)
     24     {
     25     if ($firstheader)
     26       {
     27       $firstheader = 0;
     28       print;
     29       $lastprinted = $_;
     30       $lastwascut = 0;
     31       }
     32     $_=<STDIN>;       # Remove a blank that follows
     33     next;
     34     }
     35 
     36   # Count runs of empty lines
     37 
     38   if (/^\s*$/)
     39     {
     40     $blankcount++;
     41     $lastwascut = 0;
     42     next;
     43     }
     44 
     45   # If a chunk of lines has been cut out (page footer) and the next line
     46   # has a different indentation, put back one blank line.
     47 
     48   if ($lastwascut && $blankcount < 1 && defined($lastprinted))
     49     {
     50     ($a) = $lastprinted =~ /^(\s*)/;
     51     ($b) = $_ =~ /^(\s*)/;
     52     $blankcount++ if ($a ne $b);
     53     }
     54 
     55   # We get here only when we have a non-blank line in hand. If it was preceded
     56   # by 3 or more blank lines, read the next 3 lines and see if they are blank.
     57   # If so, remove all 7 lines, and remember that we have just done a cut.
     58 
     59   if ($blankcount >= 3)
     60     {
     61     for ($i = 0; $i < 3; $i++)
     62       {
     63       $next[$i] = <STDIN>;
     64       $next[$i] = "" if !defined $next[$i];
     65       $next[$i] =~ s/\x1b\[\d+m//g;   # Remove screen controls "ESC [ number m"
     66       $next[$i] =~ s/.\x8//g;         # Remove "char, backspace"
     67       }
     68 
     69     # Cut out chunks of the form <3 blanks><non-blank><3 blanks>
     70 
     71     if ($next[0] =~ /^\s*$/ &&
     72         $next[1] =~ /^\s*$/ &&
     73         $next[2] =~ /^\s*$/)
     74       {
     75       $blankcount -= 3;
     76       $lastwascut = 1;
     77       }
     78 
     79     # Otherwise output the saved blanks, the current, and the next three
     80     # lines. Remember the last printed line.
     81 
     82     else
     83       {
     84       for ($i = 0; $i < $blankcount; $i++) { print "\n"; }
     85       print;
     86       for ($i = 0; $i < 3; $i++)
     87         {
     88         $next[$i] =~ s/.\x8//g;
     89         print $next[$i];
     90         $lastprinted = $_;
     91         }
     92       $lastwascut = 0;
     93       $blankcount = 0;
     94       }
     95     }
     96 
     97   # This non-blank line is not preceded by 3 or more blank lines. Output
     98   # any blanks there are, and the line. Remember it. Force two blank lines
     99   # before headings.
    100 
    101   else
    102     {
    103     $blankcount = 2 if /^\S/ && !/^Last updated/ && !/^Copyright/ &&
    104       defined($lastprinted);
    105     for ($i = 0; $i < $blankcount; $i++) { print "\n"; }
    106     print;
    107     $lastprinted = $_;
    108     $lastwascut = 0;
    109     $blankcount = 0;
    110     }
    111   }
    112 
    113 # End
    114