From: Eric Schwartz <emschwar@...>
Date: 2002-11-16T02:43:28+09:00
Subject: Re: Problem writing to file after closing $stdout & $stderr

ahoward <ahoward@fsl.noaa.gov> writes:
> perhaps something in the parent is writing to stderr/out?  i ask because this
> works fine for me

Why shouldn't the parent write to stderr/out?  The child should
inherit its own copy of all open file descriptors (which at this point
is just stdin, stdout and stderr).  Did you mean the child may be
writing?

Here's a minimal example:

1  puts "before fork"
2  fork {
3  puts "in child"
4  logfile = File.open('/tmp/logfile','w')
5  logfile.sync=true
6  logfile.puts "before cleosing file descriptors"
7  $stdout.close
8  $stdout = nil
9  logfile.puts "closed $stdout"
10 $stderr.close
11 $stderr = nil
12 logfile.puts "closed $stderr"
13 $stdin.close
14 $stdin = nil
15 logfile.puts "closed $stdin"
16 }
17 puts "after fork, in parent"

This crashes at the line "$stdout = nil" with:

/tmp/test.rb:8: closed stream (IOError)
        from /tmp/test.rb:3:in 'fork'
        from /tmp/test.rb:3

This is what I don't get: I closed $stdout on the line before.  Why
does it appear to be writing to a closed stream on line 8?  I get the
same result if I try to replace line 8 with

$stdout = $stderr

-=Eric
-- 
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