Capture return value from python

Question

I have a shell script TestNode.sh. This script has content like this:

port_up=$(python TestPorts.py)
python TestRPMs.py

Now, I want to capture the value returned by these scripts.

TestPorts.py

def CheckPorts():
 if PortWorking(8080):
 print "8080 working"
 return "8080"
 elif PortWorking(9090):
 print "9090 working"
 return "9090"

But as I checked the answers available, they are not working for me. The print is pushing the value in variable port_up, but I wanted that print should print on the console and the variable port_up should get the value from return statement. Is there a way to achieve this?

Note: I don't wish to use sys.exit(). Is it possible to achieve the same without this?

Answer 1

but I wanted that print should print on the console and the variable port_up should get the value from return statement.

Then don't capture the output. Instead do:

python TestPorts.py
port_up=$? # return value of the last statement
python TestRPMs.py

---

You could do:

def CheckPorts():
 if PortWorking(8080):
 sys.stderr.write("8080 working")
 print 8080

But then I am not very happy to print "output" to stderr either.

Alternatively, you could skip printing that "8080 working" message in python script and print it from the shell script.

def CheckPorts():
 if PortWorking(8080):
 return "8080"

and:

port_up=$(python TestPorts.py)
echo "$port_up working"
python TestRPMs.py

• Aakash Goyal: That just tells whether the script execution was successful or not.
• P.P: If you want to use the exit value (to get port num), I don't see another way (shorting of writing to a file or parsing the python script's output etc).
• Aakash Goyal: Hmm, then I have to redesign my solution. Thanks :)
• P.P: I have updated with some more suggestions. It's not too tricky to solve this. But it's upto you decide which one you prefer.

Answer 2

To return an exit code from a Python script you can use sys.exit(); exit() may also work. In the Bash (and similar) shell, the exit code of the previous command can be found in $?.

However, the Linux shell exit codes are 8 bit unsigned integers, i.e. in the range 0-255, as mentioned in this answer. So your strategy isn't going to work.

Perhaps you can print "8080 working" to stderr or a logfile and print "8080" to stdout so you can capture it with $().