Get system encoding. Most of this code is a part of salt/__init__.py

def get_system_encoding():
    '''
        Get system encoding. Most of this code is a part of salt/__init__.py
    '''
    # This is the most trustworthy source of the system encoding, though, if
    # salt is being imported after being daemonized, this information is lost
    # and reset to None
    encoding = None

    if not sys.platform.startswith('win') and sys.stdin is not None:
        # On linux we can rely on sys.stdin for the encoding since it
        # most commonly matches the filesystem encoding. This however
        # does not apply to windows
        encoding = sys.stdin.encoding

    if not encoding:
        # If the system is properly configured this should return a valid
        # encoding. MS Windows has problems with this and reports the wrong
        # encoding
        import locale
        try:
            encoding = locale.getdefaultlocale()[-1]
        except ValueError:
            # A bad locale setting was most likely found:
            #   https://github.com/saltstack/salt/issues/26063
            pass

        # This is now garbage collectable
        del locale
        if not encoding:
            # This is most likely ascii which is not the best but we were
            # unable to find a better encoding. If this fails, we fall all
            # the way back to ascii
            encoding = sys.getdefaultencoding()
        if not encoding:
            if sys.platform.startswith('darwin'):
                # Mac OS X uses UTF-8
                encoding = 'utf-8'
            elif sys.platform.startswith('win'):
                # Windows uses a configurable encoding; on Windows, Python uses the name "mbcs"
                # to refer to whatever the currently configured encoding is.
                encoding = 'mbcs'
            else:
                # On linux default to ascii as a last resort
                encoding = 'ascii'
    return encoding