From: Tim Hunter <TimHunter@...>
Date: 2008-10-18T09:00:14+09:00
Subject: Re: Error Exception if script doesn't run

jackster the jackle wrote:
> It seems to work but not for this command, perhaps since scp gets 
> executed (but does not complete) the system variable is not false?
> 
> [code]
> `scp -i /home/jsmith/.ssh/id_rsa /files*.tar jsmith@172.20.1.1:`
> [/code]
> 
> The error code I get when I run the script manually is as follows 
> because 172.20.1.1 is no longer on the network:
> 
>    ssh: connect to host 172.20.1.1 port 22: No route to host
>    lost connection
> 
> I was hoping the system variable would trip when this command fails?
> 
> jack

In the general case, when a command succeeds it returns 0 and when it 
fails it returns something else. However, this is a convention, not a 
rule. It is entirely possible for a command to fail and still return 0. 
If so, you can't determine if it fails by simply checking the return 
code. I have no idea whether or not scp returns non-0 on failure. You 
can check by running it yourself in a shell. Immediately after it fails 
enter 'echo $?'. This will show you the exit status. For example:

~$ ls test.rb
test.rb
~$ echo $?
0
~$ ls nothere
ls: nothere: No such file or directory
~$ echo $?
1

If your scp command returns 0 in this case then the only way to detect 
that it failed is to inspect the message, which it probably is writing 
to stderr.

More information about exit status and $? can be found on the Internet.

-- 
RMagick: http://rmagick.rubyforge.org/