Errors with Ruby and File.open

What is the error message you're getting: NoMethodError: undefined method+' for nil:NilClass` ?

If yes, then Socket.gethostname().gsub!(/[[:space:].]/,"") is returning nil

How do you create your Socket ? You could try with a fully qualified domain name, i.e. "myhost.mydomain.com" instead of "myhost".

What name should your log file have ?

First of all, there's no really compelling reason to strip dots from hostnames. "www.example.com.log" is a better filename than "wwwexamplecom.log". So my recommendation would be to use this:

def log_execution hostname = (Socket.gethostname() || "localhost") File.open(hostname + ".log", "a") do |f| f.puts( " [" + Time.new.to_s + "] " + File.basename($0) + " " + $*.join(" ") ) end end 

But if you really must, then use this:

def log_execution hostname = (Socket.gethostname() || "localhost") File.open(hostname.gsub(".", "") + ".log", "a") do |f| f.puts( " [" + Time.new.to_s + "] " + File.basename($0) + " " + $*.join(" ") ) end end 

Essentially, this block of code just logs the name of the command being run and the command line arguments used to invoke it. Also note, I renamed and reformatted the method to use standard Ruby coding style. The original was really awful.

There is more than the ruby code style that you can improve:

• use gethostbyname, and rescue to a default
• open the file using a block, ensures that if something throws, the file is closed

The result would be:

require 'socket' def log_execution() logname = Socket.gethostbyname(Socket.gethostname).first rescue "localhost" File.open("#{logname}.log", 'a') do |f| f.puts(" [" + Time.new().to_s() + "] " + File.basename($0) + " " + $*.join(" ")) end end 

And then you can improve further, by not reinventing the stdlib:

require 'socket' require 'logger' # do only once in your program logname = Socket.gethostbyname(Socket.gethostname).first rescue "localhost" log = Logger.new(logname) log.level = Logger::WARN 

Then just log using the standard api:

log.info("hello!") log.warn("message!") 

If you don't like the format which looks like:

W, [2009-12-05T03:05:48.764552 #22759] WARN -- : message! 

You can use log4r, which is api compatible but has more options...