concatinating the string in each line of the file

Shell Programming and Scripting
1

how to concatenate particular string in each line of a file..

root$cat conf

check_11043
heartbeat_4345

----------

if i want to add the string "done" output of the file should be

check_11043 done
heartbeat_4345 done

2 
sed -i 's/$/ done/' conf

or (safer)

sed -e 's/$/ done/' conf > conf.done