From: stephen.hill@... (Steve Hill)
Date: 2001-07-17T19:55:19+09:00
Subject: [ruby-talk:17984] waiting for `backquotes` to finish

Hi,
I'm sure this isn't really a ruby specific question, but since I scipt
in ruby, maybe someone has a good answer...

Some of the scripting relies on some of the standard unix tools to do
its work, called using backquotes. e.g. the following facet which
processes the columns of a file previously created with grep.

`grep FOO foo.txt > foo.tmp`

flag?=false
hash=Hash.new
IO.for_each("foo.tmp") do |line|
   unless flag? do
      cols=line.split
      (0...cols).each {|i| hash[i]=Bar.new}
   end

   cols=line.split
   hash.each {|k,v| v.process(cols[i]) }  #A
end

The problem is that the script may fail at the line marked A because
the file "foo.tmp" has either not been written at all, or has not been
completely written.

The first problem can be solved by inserting the following section
after the grep.

while !File.stat?("foo.tmp").size? 
   sleep 0.001
end

Does anyone know how to test that "foo.tmp" has been completely
written?

Best regards

Steve