How would you replace the headers in a CSV file?

Question

I'm brand new to ruby, and fairly new to programming.

How would you change the headers of a csv file?

foo, bar, foobar
1,   2,   3,
4,   5,   6,
7,   8,   9,

Change to:

herp, derp, herpaderp
1,    2,    3,
4,    5,    6,
7,    8,    9,

I have found this question, however it doesn't really apply since I'm using the built in 'csv' library instead of the older 'fastcsv' library. (using ruby 2.0.0 on Mac OSX)

What I've tried.

require 'csv'
@filename = ARGV[0]
new_headers = ["herp", "derp", "herpaderp"]

origional_csv = CSV.read(@filename, {headers: true, return_headers: true })
headers = CSV.open(@filename, 'r', :headers => true).read.headers
puts headers

#Change headers to new_headers ?

Calling test.rb from the command line with foo.csv file

$ ruby test.rb foo.csv
foo, bar, foobar

tadman · Accepted Answer · 2014-04-05 18:52:41Z

1

You don't even need to do this with the CSV library. Just change the first line of the file, output the rest the same:

lines = File.readlines(@filename)
lines.shift
lines.unshift(["herp", "derp", "herpaderp"].join(',') + "\n")
puts lines.join('')

answered Apr 5, 2014 at 18:52

tadman

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2 Comments

Arup Rakshit Over a year ago

I think, update in the same file is not possible partially. Am I right? need to copy data from one file, after processing data, sent those data to a new file..

tadman Over a year ago

Update in place isn't possible unless the header text is exactly the same length. It's usually best to re-write to a different file anyway in case you screw something up.

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