I am trying to tag a number onto the front of a unique field in a datafile. At the moment i can do this to the second field in a file because it is always preceeded by a D and a pipe delimeter ie 'D|'. There fore i am using this where pIncrese is the number to be put on the front sed "s/^D|\(.*\)|/D|${pIncrease}\1|/" \ I now want to be able to do the same thing but to the third field in another file, i tried this unsucessfully sed "s/^D|\(.*\)|\(.*\)|/D|\(.*\)| \ ${pIncrease}\1|/" the third fourth fifth etc fields can only be identified by the number of '|' chracters preceeding them. Can anyone help!

awk is easier for targeting selected fields.  I am assuming that you have fields delimited by pipe characters. pIncrease=123 awk -F\| -v incr=$pIncrease '\ BEGIN {OFS="|"} {$3=incr $3  print}' filein