get the return code when piping something to a python script?

[Jeff Schwab]

mhenry1384 wrote:
> On WinXP, I am doing this
> 
> nant.exe | python MyFilter.py
> 
> This command always returns 0 (success) because MyFilter.py always
> succeeds.

...

> How do I set the return code from MyFilter.py based on the return of
> nant.exe?  Is this possible?  I have googled around for an hour wihtout
> success.  I understand that I could have MyFilter.py call "nant.exe",
> but for various reasons, that's not idea for my situation.

It's probably not possible.  The reason is that the left-most process in 
the pipe is not guaranteed to exit before the right-most process, so in 
general, there may not be any return code to get.  If you're not too 
attached to cmd.exe, you might want to try a different shell that can 
provide a similar effect to what you requested.  For example, in bash, 
you might set the pipefail option.


$ ls nonesuch | ./return_zero.py
ls: nonesuch: No such file or directory
$ echo $?	# Print the status of the last foreground pipe.
0
$ set -o pipefail
$ ls nonesuch | ./return_zero.py
ls: nonesuch: No such file or directory
$ echo $?
2