Question

I have a text file with several different sections. Each section has a header followed by the actual data. For example:

Header1
x,y,z
x,y,z
x,y,z
Header2
a,b,c
a,b,c
a,b,c

I want to read through the file in one pass and do different things with the data present under each section. I know how to parse the data, but I’m having trouble figuring out how to code the logic for “Do this until hitting Header2, then do something else until Header3, etc.”

I’m using ruby, and I haven’t really come across any examples of doing this. Any suggestions?

Answer 1

At the simplest you could do something like this:

# Process lines for header1
def do_header1(line)
  puts line.split(/,/).join("|")
end

# Process lines for header2
def do_header2(line)
  puts line.split(/,/).map{ |e| e.upcase}.join(",")
end

header1 = false
header2 = false

# Main loop
File.open("file.txt").each_line do |line|
  if line.chomp == 'Header1' # or whatever match for header1
    header1 = true
    header2 = false
    next
  end
  if line.chomp == 'Header2' # or whatever match for header2
    header1 = false
    header2 = true
    next
  end

  do_header1(line) && next if header1
  do_header2(line) && next if header2

end

If the number of headers becomes too high, you can start tracking headers with an integer:

header = -1

# Main loop
File.open("file.txt").each_line do |line|
  if line.chomp == 'Header1' # or whatever match for header1
    header = 1
    next
  end
  if line.chomp == 'Header2' # or whatever match for header2
    header = 2
    next
  end

  do_header1(line) && next if header == 1
  do_header2(line) && next if header == 2

end