Put an * between the number 5 and 6

 

        echo '12345678901234567890'| sed  -e 's/^.\{5\}/&*/'
12345*678901234567890

Put a comma between each number

 

        echo "1234567890" |sed  -e 's/./&,/g' -e 's/,$//'
1,2,3,4,5,6,7,8,9,0

Put comma after every 2, if not even then last number exist by itself

 

        echo "1234567890" |sed  -e 's/../&,/g' -e 's/,$//'
12,34,56,78,90

Double space the data in file data1

 

                sed G data1

 

Triple space the data file file data1

                sed  'G;G' data1

 

Single space a double spaced file

 

                sed 'n;d' data1

 

Dos to Linux conversion

 

                sed 's/.$//' DOSfile >Linuxfile