Changing strings at the beginning of a large file

Specific Domains Data
12

You could process the whole header line also as follows:

open(file, "r+") do io
    str1 = readline(io) 
    str2 = replace(str1,"column" => "col")
    str2 = rpad(str2, length(str1)-2) * "\n"
    seekstart(io)
    write(io, str2)
end