From: Mark Wilson <mwilson13@...>
Date: 2003-08-23T08:36:43+09:00
Subject: Re: Line wrapping

Here's some C code to do line wrapping (written by Joseph K. Myers) 
quickly, efficiently and simply. The code is presented verbatim:

=begin
/* An explanation is more troublesome than the problem. */

int main(int argc, char **argv) {
         char b[4096]; int l=0, m=-1, m1=-1, s1=0, c, i, s, w;
         if (argc < 2 || sscanf(argv[1], "%3d", &w) < 1)
                 w = 72;
         while ((s=read(0, b, m == -1 ? 4096 : m)) > 0) {
                 for (i=0; i<s; i++) {
                         c = b[i];
                         if (c == '\n')
                                 l=0, m=-1;
                         else {
                                 if (c == ' ' || c == '\t' || c == '\r')
                                         m = i;
                                 if (++l > w && m != -1) {
                                         b[m] = '\n';
                                         l = i - (i < m ? m-s1 : m);
                                         m = -1;
                                 }
                         }
                 }
                 if (m1 != -1)
                         write(1, &b[m1], s1-m1);
                 write(1, b, m == -1 ? s : m);
                 m1=m, s1=s;
         }
         if (m != -1)
                 write(1, &b[m], s1-m);
         return s;
}
=end

I was planning on wrapping Ruby around this after I learned enough C, 
Swig and Ruby, but perhaps someone else would like to do it.

It can also be called by system:

`wrap < infile > outfile`

or, if synchronization is needed:

require 'shell'
shell = Shell.new
shell.transact do
`wrap < infile > outfile`
end

Regards,

Mark