Assign the value of shell command line's output to a Vaiable in python

Question

I have a file with the below contents.

[oracle@hostname POST_DB_REFRESH_VALIDATIONS]$ cat .DB_Creds.txt
DEW:SYSTEM:ss2021:NPDOR
STW:SYSTEM:ss2021:NPDOR

When i run the below command in shell I am getting exact output as SYSTEM

[oracle@hostname POST_DB_REFRESH_VALIDATIONS]$ grep DEW .DB_Creds.txt | awk -F':' '{print $2}'
SYSTEM

whereas when i run the same in python3 command line using subprocess, i am getting the output as below.

Python 3.6.8 (default, Sep 26 2019, 11:57:09)
[GCC 4.8.5 20150623 (Red Hat 4.8.5-39)] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import subprocess
>>> output = subprocess.check_output("grep DEW .DB_Creds.txt | awk '{print $2}'", shell=True)
>>> print(output)
    b'SYSTEM\n'

I just want it as SYSTEM, not with any other special characters.

chepner · Accepted Answer · 2020-12-07 14:49:08Z

1

output has type bytes. You want to first decode that to a value of type str, then strip the trailing newline.

>>> print(output.decode().strip())
SYSTEM

You can observe the differences made by the method calls:

>>> output
b'SYSTEM\n'
>>> output.decode()
'SYSTEM\n'
>>> output.decode().strip()
'SYSTEM'

decode treats the bytes value as the UTF-8 encoding of a string by default, but that assumption is valid since you have plain ASCII text.

answered Dec 7, 2020 at 14:49

chepner

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