Python does not get environment variable when using cron.

John Nagle nagle at animats.com
Mon Aug 18 06:25:11 CEST 2008


Stephen Cattaneo wrote:
> Hello all,
> 
> I am attempting to execute an automated test (written in Python) via
> cron.  I have to check the HOSTNAME variable as part of the test, oddly
> under cron the HOSTNAME environment variable is not in the os.environ
> dictionary.  I know that cron runs in a subshell that does not have all
> of the normally set environment variables.  HOSTNAME is not one of those
> variables, it is set even in cron's subshell.  Why doesn't python get
> this variable?  Is this a bug in python2.4?  

    Cron doesn't normally use a shell at all.  It just runs the
requested program in a subprocess. So there's no shell involved,
and you don't get a shell-type user environment.  If you have
a crontab line like

10 3 * * * /usr/bin/python someprogram.py

there's no shell.  You can try

10 3 * * * /bin/sh /usr/bin/python someprogram.py

    which will load a shell, which in turn will load Python.

Or, in Python, you can use "socket.gethostname()", which will
get you the host name used for networking purposes.

					John Nagle



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