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I need to import a large table of data that arrives in fixed-width text format, and a few related smaller pieces that also come in different fixed-width formats.
I know that I can write a bit of code that unpacks lines based on an array of lengths, but is there anything more flexible out there? The smaller pieces in particular seem to change occasionally, and I'd rather not lock format details into code.
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Parsing fixed-width fields in Ruby/Rails1 Reply
If the goal is just to externalize the configuration, there are several implementation strategies (yaml, arguments to a function, additional parameters if it's a rails controller etc).
This is an example of using command line paramters:
#!/usr/bin/env ruby
unless 3 == ARGV.size
puts "#$0 <field-widths> <input-file> <output-file>"
exit -1
end
field_widths = ARGV[0].split(',').map &:to_i
input_file = ARGV[1]
output_file = ARGV[2]
field_pattern = "A#{field_widths.join('A')}"
outp = File.open(output_file,"w")
File.foreach filename do |line|
row = line.unpack field_pattern
outp.puts row.join "\t"
end
outp.close
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