Add Extract A Column Of Data From A CSV File as a ruby TIL

ruby/extract-a-column-of-data-from-a-csv-file.md

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+# Extract A Column Of Data From A CSV File
+
+Let's say I have just downloaded a medium-sized CSV of data onto my hard drive.
+I want to exact one column of data from that CSV to inject into some other
+tool/process.
+
+Here is how I'd go about doing that with Ruby.
+
+```ruby
+require 'csv'
+
+filename = "#{Dir.home}/Downloads/file.csv"
+column_index = 2 # zero-indexed column of interest
+
+# an array of collecting the values I want to extract
+col_data = []
+
+# read in the CSV into memory
+csv_data = CSV.read(filename)
+
+# pop headers out of the top of the array
+csv_data.shift
+
+# grab the column of interest from each row
+csv_data.each { |row| col_data << row[column_index] }
+
+# do something with the extract column of data
+comma_separated_list = col_data.join(', ')
+system "command -v pbcopy >/dev/null 2>&1 && echo '#{comma_separated_list}' | pbcopy"
+```
+
+All but the last two lines are pretty standard. We identify the file and column
+of interest. Read in the CSV from that file and ditch the headers. Then we grab
+that column's value for every entry in the CSV.
+
+Then we need to do something with that data.
+
+In my case, I want to turn those values into a comma-separated list and put it
+on my clipboard. Those last two lines do just that.