sed(1) -i -e ?s/class/enum/? ./billing-method.ts
stream editor for filtering and transforming text
-i[SUFFIX], --in-place[=SUFFIX]

       edit files in place (makes backup if extension supplied)
-e script, --expression=script

       add the script to the commands to be executed
If no -e, --expression, -f, or --file option is given, then the first non-option argument is taken as the
sed script to interpret.  All remaining arguments are names  of  input  files;  if  no  input  files  are
specified, then the standard input is read.
source manpages: sed