subprocess problem

[Günther Dietrich]

Am 09.02.17 um 18:16 schrieb Andreas Paeffgen:
> I guess which does not return an error code.

In fact, id does return a return code. Here an example:

| honk:~ gdie$ which bash; echo $?
| /bin/bash
| 0
| honk:~ gdie$ which wzlbrmpf; echo $?
| 1

It is 0 on success, 1 for a failure. Exactly the result I would expect
from an unixoid program.


On Ubuntu 16.04, 'man which' tells of three possible exit states: 0, 1
and 2.
On Mac OS, the return codes are not documented. It seems, there are only
0 (success) and 1 (failure).

Normally, on unixoid operating systems, return code 0 indicates success,
anything else non-success, failure or error.


> If it does not find
> anything, the return is just blank. If it finds something, the path is
> returned.

That is the result on STDOUT. It is _not_ the return code!


> So the change of code did not help, because there is just no error message.

Do you expect an error message, or a return code? An error message would
-- normally -- appear on STDERR.


> Could there be a $path problem in the subprocess started inside the binary?

That's for sure. I already had this problem with py2exe. I solved it by
passing a directory containing a suitable PATH entry to the env argument
of subprocess.Popen(). Problem gone.


If you call 'python myscript.py' on the shell command line, the python
script will inherit a copy the shell's environment.
If you start a frozen python script, there is no shell's environment, it
could inherit. It is up to the tool you used to freeze the script
(cx_freeze, py2exe, etc.), which environment contents it will see.



Best regards,

Günther