Shell Programming and Scripting

 fmt -w 78 file > file_new

Here is the first paragraph of type 1 which is very long and should be formated.

%
Here is the second paragraph of type 2 which should stay as it is.
%

Here is the third paragraph of type 1 which is very long and should be formated.

%
Here is the fourth paragraph of type 2 which should stay as it is.
%

...

 fmt -w 78

Here is the first paragraph of type 1 which is very 
long and should be formated.

%
Here is the second paragraph of type 2 which should stay as it is.
%

Here is the third paragraph of type 1 which is very 
long and should be formated.

%
Here is the fourth paragraph of type 2 which should stay as it is.
%

...

perl -ne '$s.=$_; if (/^$/) {if ($prev ne "%") {open(OUT,"|fmt -w 78"); print OUT $s; close OUT;} else {print $s}; $s=""}; chomp($prev=$_);' file

#!/usr/bin/env bash

# @(#) s1	Demonstrate perl wrap paragraphs.

# Utility functions: print-as-echo, print-line-with-visual-space, debug.
# export PATH="/usr/local/bin:/usr/bin:/bin"
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 divepm
divepm -q -i p1

FILE=${1-data1}

pl " Input data file $FILE:"
cat $FILE

pl " perl code:"
cat p1

pl " Results:"
./p1 $FILE

exit 0

% ./s1

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
divepm (local) 1.4
 1.06	warnings
 1.04	strict
 2006.1117	Text::Wrap

-----
 Input data file data1:
%
         1         2         3         4         5         6         7         8
12345678901234567890123456789012345678901234567890123456789012345678901234567890
%

Here is the first paragraph of type 1 which is very 
long and should be formatted.

%
Here is the second paragraph of type 2 which should stay as it is.
%

Here is the third paragraph of type 1 which is very 
long and should be well formatted.

%
Here is the fourth paragraph of type 2
which should stay as it is.
%


-----
 perl code:
#!/usr/bin/env perl

# @(#) p1	Demonstrate reading paragraphs, re-formatting.

use warnings;
use strict;
use Text::Wrap;

my (@p);

$/ = "\n\n";    # Records are paragraphs, ending with empty line.
$Text::Wrap::columns = 78;

while (<>) {
  if (m{^%}) {
    print;
  }
  else {
    @p = split( /\n/, $_ );	# split paragraph into array of lines
    print wrap( '', '', @p );
    print "$/";
  }
}

exit(0);


-----
 Results:
%
         1         2         3         4         5         6         7         8
12345678901234567890123456789012345678901234567890123456789012345678901234567890
%

Here is the first paragraph of type 1 which is very long and should be
formatted.

%
Here is the second paragraph of type 2 which should stay as it is.
%

Here is the third paragraph of type 1 which is very long and should be well
formatted.

%
Here is the fourth paragraph of type 2
which should stay as it is.
%