Shell Programming and Scripting

awk 'BEGIN {FS="Class"} (NR > 2) && (X != $1) { print "" } { X = $1 } 1' input_file > output_file

awk '/^[0-9]/ && (X != $1) { print "" } { X = $1 } 1' input_file > output_file

Class
Number Position Range

1 Initial 50
1 Initial 50

2 Terminal 150
2 Terminal 20
2 Single 10

3 Single 20

4 Double 50

5 Initial 50
5 Initial 60

Class
Number Position Range

1 Initial 150

2 Terminal 250
2 Terminal 200

3 Single 20

4 Double 50
4 Single 100

5 Initial 100

#!/bin/bash
NN=""
outputFile="/tmp/output"
while read N LINE # Puts the first field (the number) in N and the rest in LINE
do
    [ "$NN" != "$N" ] && echo # insert newline if the N is different than the previous value
   # the && executes the next command if the return of the previous one returned TRUE
   # the "!" negates the "=" and  "[ ... ]" means "test if"
    echo "$N $LINE"
    NN=$N
done < $inputfile > $outputfile

my $flag = "-1.1";
while(<DATA>){
	my @tmp = split(" ",$_,2);
  if (($tmp[0] ne $flag) && /^[0-9]/){
  	print "\n";
  	$flag = $tmp[0];
  }
  print;
}
__DATA__
Class
Number Position Range
1 Initial 50 
1 Initial 50
2 Terminal 150
2 Terminal 20 
2 Single 10 
3 Single 20
4 Double 50
5 Initial 50
5 Initial 60

Class
Number Position Range
1 Initial 150 
2 Terminal 250
2 Terminal 200 
3 Single 20
4 Double 50
4 Single 100 
5 Initial 100