Add the ERL_SYS_SHELL env variable to point to system shell for os:cmd()

[yarisx]

A fix for #8944

[github-actions]

CT Test Results

    2 files     69 suites   1h 4m 55s ⏱️
1 534 tests 1 291 ✅ 242 💤 1 ❌
1 748 runs  1 473 ✅ 274 💤 1 ❌

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Results for commit 98e2413.

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// Erlang/OTP Github Action Bot

[garazdawi]

Hello! Thanks for the PR!

The variable should be a kernel configuration parameter that is set to the correct value when kernel is started. It also needs to be documented here and a testcase needs to be added to os_SUITE.

[garazdawi]

Thanks for the update! I've pushed a commit that renames the variable to os_cmd_shell which I think better describes what it does and also moved the shell detection logic to happen when we start instead of everytime we do os:cmd.

Would you mind updating the docs of os:cmd/2 to point to the docs for the configuration parameter so that users know where to find it?

Feel free to squash my commit into yours if you agree with my changes.

[yarisx]

I'm a bit confused by the test results. As I see one subtest in shell_history_custom_error/1 test failed with the timeout, but a similar subtest passed just fine. Moreover I don't see how this part of the functionality can be affected by my changes, and locally the test passed just fine. Could you give me a hint on what might cause the test to fail?

[garazdawi]

I think there might be a race in that testcase that you've had the misfortune of hitting, so you can ignore that.

However, the os:internal_init_os_cmd/1 should not need to be called in all those test suites. The testcase needs to make sure that it resets the state (as you have done). Why did you add them?

Also could you please add a test that uses ?CT_PEER to start a new code where the config parameter is set at startup to see that that works. I don't think os:cmd is used anywhere when booting Erlang so we should be safe.

[yarisx]

I added os:internal_init_os_cmd/1 because locally the tests that contain os:cmd/2 (at least some of them) crashed with badmatch at {ok, Shell} = application:get_env() in os:mk_cmd/2.
I will add the test with ?CT_PEER

[garazdawi]

I added os:internal_init_os_cmd/1 because locally the tests that contain os:cmd/2 (at least some of them) crashed with badmatch at {ok, Shell} = application:get_env() in os:mk_cmd/2.

How odd, can you remove them and see if that happens in github ci as well?