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Full Discussion: Ruby: "Can't convert nil into String" error
Top Forums Programming Ruby: "Can't convert nil into String" error Post 302767857 by Elvirnith on Thursday 7th of February 2013 03:20:10 PM
Old 02-07-2013
Ruby: "Can't convert nil into String" error
Hi there,

I'm relatively new to ruby and I'm trying to put together this script to process cron jobs on a server. It's almost working, except I can't figure out what exactly is wrong and how to fix it. Can anyone point me in the right direction?

Here's what I have so far:

Code:
require 'rubygems'
require 'crontab-parser'

start_time = Time.parse(ARGV[0])
end_time = Time.parse(ARGV[1])

File.open('/root/flagged_cron_jobs.log', 'w+') do |f2|

crontab_data = File.readlines(ARGV[2]).select {|line| line =~ /^[0-9*]/}
cron  = CrontabParser.new(crontab_data.join("\n"))
(start_time..end_time).each do |timestamp|
  next unless timestamp.sec.to_i == 0
  cron.each do |cron_entry|
Dir["/var/spool/cron/*"].each do |file|
  username = file.split("/").last
  crontab = CrontabParser.new(File.read(file))
  puts "User: #{username}"
    if cron_entry.should_run?(timestamp)
      f2.puts "#{timestamp}\t#{cron_entry.cmd}"

        end
      end
    end
  end
end

Here's the error:

Code:
cron_parse.rb:9:in `readlines': can't convert nil into String (TypeError)
	from cron_parse.rb:9
	from cron_parse.rb:7:in `open'
	from cron_parse.rb:7

Command being executed is like so:

Code:
ruby cron_parse.rb "Thurs Feb 7 01:00 UTC 2013" "Thurs Feb 7 01:14 UTC 2013"

I suspect it's because of the addition of
Code:
 crontab = CrontabParser.new(File.read(file))

in relation to
Code:
cron  = CrontabParser.new(crontab_data.join("\n"))

but I'm not really sure of how to deal with this.
Last edited by jim mcnamara; 02-07-2013 at 04:53 PM..
 

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LEARN ABOUT DEBIAN

ruby-switch

RUBY-SWITCH(1)															    RUBY-SWITCH(1)

NAME

       ruby-switch - switch between different Ruby interpreters

USAGE

       ruby-switch --list

       ruby-switch --check

       ruby-switch --set RUBYVERSION

       ruby-switch --auto

DESCRIPTION

       ruby-switch can be used to easily switch to different Ruby interpreters as the default system-wide interpreter for your Debian system.

       When run with --list, all supported Ruby interpreters are listed.

       When --check is passed, ruby-switch will check which Ruby interpreter is currently being used. If the settings are inconsistent -- e.g.
	 `ruby` is Ruby 1.8 and `gem` is using Ruby 1.9.1, ruby-switch will issue a big warning.

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       the default implementations for the following programs: ruby, gem, irb, erb, testrb, rdoc, ri.

       ruby-switch --set auto will make your system use the default Ruby interpreter currently suggested by Debian.

OPTIONS

       -h, --help
	   Displays the help and exits.

A NOTE ON RUBY 1.9.x
       Ruby uses two parallel versioning schemes: the `Ruby library compatibility version' (1.9.1 at the time of writing this), which is similar
       to a library SONAME, and the `Ruby version' (1.9.3 is about to be released at the time of writing).

       Ruby packages in Debian are named using the Ruby library compatibility version, which is sometimes confusing for users who do not follow
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COPYRIGHT AND AUTHORS

       Copyright (c) 2011, Antonio Terceiro <terceiro@debian.org>

       This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by
       the Free Software Foundation, either version 3 of the License, or (at your option) any later version.

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