How to get retune code of function when using log redirection in Shell?

Question

In My shell scripts1, It works.：

test1.sh

python main.py
if [[ $? -ne 0 ]]
then
exit
fi

test2.sh

python main.py 2>&1 | tee log.txt 
if [[ $? -ne 0 ]]
then
exit
fi

Script 2 is failed. How could I get the return code of python-call main in test2.sh？

score 2 · Answer 1 · answered Aug 29 '19 at 05:26

2

If you use more commands in one line, you need to use the PIPESTATUS to get the proper return code for each command.

For example:

Python code:

import sys


def exit_with_code():
    sys.exit(5)


exit_with_code()

Shell script:

python3 test.py  2>&1 | tee log.txt
echo "${PIPESTATUS[0]} ${PIPESTATUS[1]}"

Output:

5 0

It means the return code of Python script is 5 and the return code of tee is 0.

answered Aug 29 '19 at 05:26

milanbalazs

4,811
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@milanbalazs : PIPESTATUS is not defined in [Posix Shell](https://pubs.opengroup.org/onlinepubs/009695399/utilities/xcu_chap02.html) – user1934428 Aug 29 '19 at 07:22
Yes, you are right! But the questioner didn't mentioned POSIX in his question! But this problem can be solved with temp files in POSIX. – milanbalazs Aug 29 '19 at 07:25
@milanbalazs: Actually he did. He tagged it as _Shell_, and the definition of this tag says that unless another tag explicitly mentions a specific shell, a POSIX compatible solution is asked for. – user1934428 Aug 30 '19 at 06:53
I agree! Sorry, it was my mistake! I will pay more attention to tags. On the other hand, the questioner uses `Bash` so he can use the `PIPESTATUS`! :) – milanbalazs Aug 30 '19 at 06:57

score 1 · Accepted Answer · answered Aug 29 '19 at 07:28

1

You tagged your question for POSIX Shell, and AFIK, there is no way to achieve this in a POSIX Shell. However, many other shells do have a feature, which allow this.

For instance, if you could use bash, you can use PIPESTATUS, as was suggested here already. If you go for Zsh, there is a similar array named pipestatus.

If you want to go for ksh, you don't have an equivalent feature, but here is a discussion how to deal with this problem in Korn Shell.

answered Aug 29 '19 at 07:28

user1934428

19,864
7
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Sorry for this incomplete information. I can use bash and `PIPESTATUS` . Thank a alot ::::::))))))) – Donghui Sun Aug 29 '19 at 09:40

score 0 · Answer 3 · answered Aug 29 '19 at 06:10

0

You can do the redirection outside of the if and also avoid the antipattern.

if ! python main.py; then
   exit
fi 2>&1 | tee log.txt

(See Why is testing "$?" to see if a command succeeded or not, an anti-pattern?)

answered Aug 29 '19 at 06:10

tripleee

175,061
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How to get retune code of function when using log redirection in Shell?

3 Answers3