Take a closed $n$-manifold $M$ and fix a nice $n$-ball $B$ in $M$. How much information about $M$ does the set of knotted $(n-2)$-spheres of $B$ which are unknotted in $M$ give?


Question: Find cron jobs that run between given times
Answer: You can use the Ruby 1.8.7 gem "crontab-parser" to parse a crontab, and then iterate through each minute between the two timestamps, calling should_run? on every crontab entry:

require 'rubygems'
require 'crontab-parser'

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

# CrontabParser barfs on env variable setting in a crontab, so just skip them
cron_data = File.readlines(ARGV[2]).select {|line| line =~ /^[0-9*]/}
cron  = CrontabParser.new(cron_data.join("\n"))
(start_time..end_time).each do |timestamp|
  next unless timestamp.sec.to_i == 0
  cron.each do |cron_entry|
    if cron_entry.should_run?(timestamp)
      puts "#{timestamp}\t#{cron_entry.cmd}"
    end
  end
end


So, if you have a crontab.txt that looks like this:

*   *   *   *   *   foo
18  15  *   *   *   bar


Then call the script with output from date or similar and a file containing a crontab:

ruby cron_report.rb "Sat Mar 3 02:07:32 UTC 2012" "Sat Mar 3 02:21:32 UTC 2012" crontab.txt


You'll get output like this:

Sat Mar 03 15:17:00 UTC 2012    *   *   *   *   *   foo
Sat Mar 03 15:18:00 UTC 2012    *   *   *   *   *   foo
Sat Mar 03 15:18:00 UTC 2012    18  15  *   *   *   bar
Sat Mar 03 15:19:00 UTC 2012    *   *   *   *   *   foo
Sat Mar 03 15:20:00 UTC 2012    *   *   *   *   *   foo