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"
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"
scl enable python27 bash activates a python virtual environment.
You can do this from within a bash script by simply sourcing the enable script of the virtual environment, of the SCL package, which is located at /opt/rh/python27/enable
Example:
#!/bin/bash
cd /var/www/python/scripts/
source /opt/rh/python27/enable
python runAllUpserts.py >/dev/null 2>&1
Well, you could add something to your startup script to source the enable script.
Eg add to your .bash_profile (note space between initial dot and /)
. /opt/rh/python27/enable
This option sounds dangerous to me for root. I would think something like the following would be safer and more appropriate:
You can create a function that takes command line options. Think of this as an alias on steroids. Add the following to your .bashrc
python27() {
scl enable python27 “python $*”
}
Then test:
python27 –version
Python 2.7.5
This doesn’t help with your magic line in scripts, but will make it easier to call scripts:
[smccarty@keith ~]$ cat script.py
#!/usr/bin/env python27
import sys
print “Hello, World!”, sys.version
Call it normal and notice, the default installation of python is used:
[smccarty@keith ~]$ ./script.py
Hello, World! 2.6.6 (r266:84292, Sep 4 2013, 07:46:00)
[GCC 4.4.7 20120313 (Red Hat 4.4.7-3)]
Call it with our alias, and notice that Python 2.7 is used:
[smccarty@keith ~]$ python27 script.py
Hello, World! 2.7.5 (default, May 23 2013, 06:08:09)
[GCC 4.4.7 20120313 (Red Hat 4.4.7-3)]
You should try using -- instead of surrounding your command with quotes.
scl enable python27 -- ls /tmp
I was able to make a python script that uses the rh-python35 collection with this shebang:
#!/usr/bin/scl enable rh-python35 -- python
import sys
print(sys.version)
The parsing of arguments in the she-bang command is not really defined. From man execve:
The semantics of the optional-arg argument of an interpreter script vary across implementations. On Linux, the entire string following the interpreter name is passed as a single argument to the interpreter, and this string can include white space. However, behavior differs on some other systems. Some systems use the first white space to terminate optional-arg. On some systems, an interpreter script can have multiple arguments, and white spaces in optional-arg are used to delimit the arguments.
No matter what, argument splitting based on quote sis not supported. So when you write:
#!/usr/bin/scl enable python27 "ls /tmp"
It's very possible that what gets invoked is (using bash notation):
'/usr/bin/scl' 'enable' 'python27' '"ls' '/tmp"'
This is probably why it tries to open the "ls file at /etc/scl/prefixes/"ls
But it is just as likely that the shebang evaluates to:
'/usr/bin/scl' 'enable python27 "ls /tmp"'
And that would fail since it wont be able to find a command named enable python27 "ls /tmp" for scl to execute.
There's a few workarounds you can use.
You can call your script via scl:
$ cat myscript
#!/bin/bash
echo hello
$ scl enable python27 ./myscript
hello
You can also use the heredoc notation, but it might lead to subtle issues. I personally avoid this:
$ cat ./myscript
#!/bin/bash
scl enable python27 -- <<EOF
echo hi
echo \$X_SCLS
EOF
$ bash -x myscript
+ scl enable python27 --
hi
python27
You can see one of the gotcha's already: I had to write \$X_SCLS to access the environment variable instead of just $X_SCL.
Edit: Another option is two have two scripts. One that has the actual code, and the second that simply does scl enable python27 $FIRST_SCRIPT. Then you wont have to remember to enter scl ... manually.