From: David Masover <ninja@...>
Date: 2009-09-21T22:20:43+09:00
Subject: Re: Writing to STDOUT after closing controlling terminal

On Sunday 20 September 2009 08:49:56 pm Matt Bleh wrote:
> I know it's not enough justification, but doing  an "echo 1" from a
> backgrounded bash script process doesn't kill the script.

That's because your script is badly written. Try this script:

#!/bin/sh
sleep 5
echo hi || echo $! > output

This has exactly the same behavior as your Ruby script, except that you're 
only capturing the return value of that first echo command.

In other words: In a shell script (bash or otherwise), the 'echo' command does 
indeed get killed. It's just that by default, shell scripts ignore the return 
values, which means errors are silently eaten. Ruby, on the other hand, raises 
an exception when something goes wrong.

I don't like silent errors, so I usually write shell scripts that look more 
like this:

#!/bin/sh
first line &&
second line &&
third line &&
fourth line

That way, the script dies at the first error, unless I explicitly handle it.

> I understand
> that you should redirect STDOUT, but in Ruby should programmers really
> need to concern about this?

If you don't want to be concerned about this, abstract it away with some sort 
of logging class. I'm glad Ruby has the same behavior as any other language, 
when it comes to basic Unix semantics like this -- and I'm glad my output 
doesn't just silently get eaten when I close the terminal.