Function to execute an arbitrary-length BASH script from Python; always returns a CompletedProcess object.

execute_bash_script_from_python_helper.py

# Uses `strip_margin` defined here:
# https://gist.github.com/malcolmgreaves/7c9ec3407a02a3eb6d4b898bc16dc902

import subprocess


def exec_bash_script(
    script_contents: str, *, prepend_bash_shebang_if_needed: bool = True
) -> subprocess.CompletedProcess:
    script_contents = script_contents.strip()
    if len(script_contents) == 0:
        raise ValueError("Cannot supply empty string for script execution!")

    if not script_contents.startswith("#!/"):
        if prepend_bash_shebang_if_needed:
            script_contents = "#!/usr/bin/env bash\n" + script_contents
        else:
            try:
                x = script_contents[0 : script_contents.index("\n")]
            except IndexError:
                x = script_contents
            raise ValueError(f"No shebang line found in script contents:\n{x}")

    script_contents = strip_margin(script_contents)

    with NamedTemporaryFile() as tfi:
        # write docker ECR login + pull script
        tfi.close()
        with open(tfi.name, "wt") as wt:
            wt.write(script_contents)

        chmod_cmd = ["chmod", "+x", tfi.name]
        exit_code = subprocess.check_call(chmod_cmd)
        if exit_code != 0:
            raise ValueError("Could not make script executable!")

        completed = subprocess.run(tfi.name, stdout=subprocess.PIPE, stderr=subprocess.PIPE)

    completed.args = [script_contents]
    return completed