If I understand your file contents (from your two examples) and assuming that the 1st field in your input is not always Instr1:, you might want to try this slight modification to RudiC's suggestion:

Code:

#!/bin/ksh
file=${1:-file.txt}
awk '
!/^ *$/{c[$1 OFS substr($2, 50, 8)]++
}
END {	for(v in c)
		printf("%12d %s\n", c[v], v)
}' "$file" | sort -k1,1nr -k2,3

If file.txt contains you 1st sample (unsorted with blanks lines) and file2.txt contains your 2nd sample (sorted with no blank lines), the above script when invoked without operands produces the output:

Code:

           9 Instr1: 00000000
           5 Instr1: 00101000
           2 Instr1: 00000010
           2 Instr1: 00110100
           2 Instr1: 01000011
           2 Instr1: 01001111
           2 Instr1: xxxxxxxx
           1 Instr1: 00100010

and, if it is invoked with the operand file2.txt, produces the output:

Code:

          48 Instr1: 11111110
           2 Instr1: xxxxxxxx

This was written and tested using a Korn shell, but will work with any shell that uses Bourne shell syntax and understands the parameter expansions required by the POSIX standards (such as bash, dash, ksh, and zsh).

If you want to try this on a Solaris/SunOS system, change awk to /usr/xpg4/bin/awk or nawk.