How do I modify the (shell) execution environment?
Specifically, I need to modify the PATH variable. An undesirable path sabotages the execution of a remote script. The problem is that the bare-bones shell environment used by an agent does not match the environment of the logged in build user. The result is that scripts use the system python instead of a custom python. As a result, none of my installed or home-made modules are found. Consider these steps **Step 1 commands** (using custom python as the shell)
import os, sys
print('Step info in a python shell.')
print('Python executable: ' + sys.executable)
print('Shell path: ' + os.environ['PATH'])
**Step 2 commands** (using /bin/bash as a shell)
echo "Step info in a bash shell." echo "System path in Command(s) shell: $PATH" echo "Next, running a python script:" /tmp/show_paths.py**remote script contents**
#!/usr/bin/env python
import os, sys
print('Remote information.')
print('Python executable: ' + sys.executable)
print('Shell path: ' + os.environ['PATH'])
**Output of step 1**
Step info in a python shell. Python executable: /istginfra/main/python/2.7.5/ubuntu/x86_64/bin/python Shell path: /usr/local/bin:/usr/bin:/bin:/usr/local/games:/usr/games:/opt/electriccloud/electriccommander/bin:/home/build/scripts:/home/build/bin:/opt/electriccloud/electriccommander/bin**Output of step 2**
Step info in a bash shell. System path in \Command(s) shell: /usr/local/bin:/usr/bin:/bin:/usr/local/games:/usr/games:/opt/electriccloud/electriccommander/bin:/home/build/scripts:/home/build/bin:/opt/electriccloud/electriccommander/bin Next, running a python script: Remote information. Python executable: /usr/bin/python Shell path: /usr/local/bin:/usr/bin:/bin:/usr/local/games:/usr/games:/opt/electriccloud/electriccommander/bin:/home/build/scripts:/home/build/bin:/opt/electriccloud/electriccommander/bin**The logged in user environment:** (what I want to see!)
$ echo $PATH /istginfra/main/ruby/2.0.0/ubuntu/bin:/istginfra/main/python/2.7.5/ubuntu/x86_64/bin:/istginfra/main/python/2.7.5/ubuntu/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/opt/electriccloud/electriccommander/bin:/opt/electriccloud/electriccommander/bin:/home/build/scripts:/home/build/binThe interpreter cannot be hard-coded in first line of the scripts. The scripts may be run on cygwin or a redhat host. And, the location of the interpreter binary can change. So, how do I modify the environment and/or search path that Commander uses?
You could just modify the agent user's shell environment, for example .bash_profile, to make the path to the custom python directory at the front of the PATH env variable, but that might not satisfy all of your requirements.
For the past decade, we've used a strategy in our legacy (non-EC) build system which allows to have multiple tool versions on the same machine. We've ported this forward to EC, and a very simplified version of what we do is:
- Create an 'asset' property sheet on your Resource (like asset:python_2.7). We use the 'asset' decoration simply as a convention to group things. We specify the version since we have lots of them.
- In the sheet, we create a 'path' property to the executable with a value like /tools/python/2.7.5/ubuntu/x86_64/bin/python .
- In fact, we also have an 'env' property sub-sheet within the asset sheet which we use to modify the environment for a given tool, like a specific JAVA_HOME for ant, but dealing with that is a bit more complex.
Then, in our Perl code we do something like this:
my $pyPath = "/myResource/asset:python_2.7/path";
`$pyPath myCode.py`;
I suppose the shell version could be the following, as long as there are no spaces in the 'path':
$[/myResource/asset:python_2.7/path] myCode.py
In summary, this mechanism allows us to install a tool anywhere on the machine, and as long as we reference it correctly, we'll always run the correct version of the tool.
