scl enable python27 bash
I've hit a snag with a shell script intended to run every 30 minutes in cron on a Redhat 6 server. The shell script is basically just a command to run a python script.
The native version python on the server is 2.6.6 but the python version required by this particular script is python 2.7+. I am able to easily run this on the command line by using the "scl" command (this example includes the python -V command to show the version change):
$ python -V
Python 2.6.6
$ scl enable python27 bash
$ python -V
Python 2.7.3
At this point I can run the python 2.7.3 scripts on the command line no problem.
Here's the snag.
When you issue the scl enable python27 bash command it starts a new bash shell session which (again) is fine for interactive commandline work. But when doing this inside a shell script, as soon as it runs the bash command, the script exits because of the new session.
Here's the shell script that is failing:
#!/bin/bash
cd /var/www/python/scripts/
scl enable python27 bash
python runAllUpserts.py >/dev/null 2>&1
It simply stops as soon as it hits line 4 because "bash" pops it out of the script and into a fresh bash shell. So it never sees the actual python command I need it to run.
Plus, if run every 30 minutes, this would add a new bash each time which is yet another problem.
I am reluctant to update the native python version on the server to 2.7.3 right now due to several reasons. The Redhat yum repos don't yet have python 2.7.3 and a manual install would be outside of the yum update system. From what I understand, yum itself runs on python 2.6.x.
Here's where I found the method for using scl
Answer
Doing everything in one heredoc in the SCL environment is the best option, IMO:
scl enable python27 - << \EOF
cd /var/www/python/scripts/
python runAllUpserts.py >/dev/null 2>&1
EOF
Another way is to run just the second command (which is the only one that uses Python) in scl environment directly:
cd /var/www/python/scripts/
scl enable python27 "python runAllUpserts.py >/dev/null 2>&1"