Reading the first line of a file in Ruby

Question

I want to read only the first line of a file using Ruby in the fastest, simplest, most idiomatic way possible. What's the best approach?

(Specifically: I want to read the git commit UUID out of the REVISION file in my latest Capistrano-deployed Rails directory, and then output that to my tag. This will let me see at an http-glance what version is deployed to my server. If there's an entirely different & better way to do this, please let me know.)

Answer 1

This will read exactly one line and ensure that the file is properly closed immediately after.

strVar = File.open('somefile.txt') {|f| f.readline} # or, in Ruby 1.8.7 and above: # strVar = File.open('somefile.txt', &:readline) puts strVar 

Answer 2

Here's a concise idiomatic way to do it that properly opens the file for reading and closes it afterwards.

File.open('path.txt', &:gets) 

If you want an empty file to cause an exception use this instead.

File.open('path.txt', &:readline) 

Also, here's a quick & dirty implementation of head that would work for your purposes and in many other instances where you want to read a few more lines.

# Reads a set number of lines from the top. # Usage: File.head('path.txt') class File   def self.head(path, n = 1)      open(path) do |f|         lines = []         n.times do           line = f.gets || break           lines << line         end         lines      end   end end