returncode called via API in Python subprocess module always returns 0

Question

I have a flask api which triggers a bash script and get its exit code for further processing .I am using Subprocess module. But when i try to capture the return code for further processing it is always 0 even if the script failed..

for testing if i run the same piece of code using a python script it works fine

Below is my API code

@app.route("/test1", methods=['POST', 'GET'])
def testfunc1():
    path = "/home/admin/temp1"
    if request.method == "POST":
        try:
            payload = request.json
            password = payload["password"]
            password_bytes = bytes(password + '\n', encoding='utf-8')
            dpath = "/home/admin/temp1/New-folder"
            proc = subprocess.Popen(['sudo', '-S', 'sh', os.path.join(dpath,'test1.sh')], stdin=subprocess.PIPE, stdout=subprocess.PIPE, stderr=subprocess.PIPE)
            out, err = proc.communicate(input=password_bytes)
            if proc.returncode == 0:
                logger(level="exception", message=str(proc.returncode))
                response = response_handle(response="success",code=200)
                return response
            else:
                logger(level="exception", message=str(proc.returncode))
                proc = subprocess.Popen(['sudo', '-S', 'sh', os.path.join(dpath,'test1.sh')], stdin=subprocess.PIPE, stdout=subprocess.PIPE, stderr=subprocess.PIPE)
                out, err = proc.communicate(input=password_bytes)
                
            response = response_handle(response="Done",code=200)
            return response
        except Exception as err:
            logger(level="exception", message=str(err))
            response = response_handle(code=500, response=str(err))
            return response

Even my shell script fails it returns returncode as '0'

Below is my shell script

#!/bin/sh

tar -xf "/home/admin/temp1/New-folder/upgrade.tar.gz" #tar file does not exist
error_code=$?
if [ $error_code -eq 0 ]; then
        echo Untar is completed
else
        echo ERROR: {Error Code: $error_code, Error Message: Can Not Untar}
        exit $error_code
fi

below is my python code

import subprocess
import os


dpath = "/home/admin/temp1/New-Folder"
password = "password"
password_bytes = bytes(password + '\n', encoding='utf-8')
proc = subprocess.Popen(['sudo', '-S', 'sh', os.path.join(dpath,'test1.sh')], stdin=subprocess.PIPE, stdout=subprocess.PIPE, stderr=subprocess.PIPE)
out, err = proc.communicate(input=password_bytes)


print(proc.returncode)
print(out)
print (err)
if proc.returncode == 0:
    print("success")
else:
    print("fail")

Output for my python script

2
b'ERROR: {Error Code: 2, Error Message: Can Not Untar}\n'
b'tar: /home/admin/temp1/New-folder/upgrade.tar.gz: Cannot open: No such file or directory\ntar: Error is not recoverable: exiting now\n'
fail

Output for my api

api/api_server.py:3717 :: 0 #return type
and reponse is success

Not sure what is wrong

please help :)

You forgot to `wait`. Didn't you ask the same question twice already? — tripleee, Feb 23 '22 at 13:14
And again, repeat the guidance from the `subprocess` documentation: Don't use bare `Popen` if you don't have to. — tripleee, Feb 23 '22 at 13:17
Tangentially, [Why is testing ”$?” to see if a command succeeded or not, an anti-pattern?](https://stackoverflow.com/questions/36313216/why-is-testing-to-see-if-a-command-succeeded-or-not-an-anti-pattern) — tripleee, Feb 23 '22 at 13:18

returncode called via API in Python subprocess module always returns 0

0 Answers0