FAQ 8.37 How do I find out if I'm running interactively or not?

Discussion in 'Perl Misc' started by PerlFAQ Server, Feb 19, 2011.

  1. This is an excerpt from the latest version perlfaq8.pod, which
    comes with the standard Perl distribution. These postings aim to
    reduce the number of repeated questions as well as allow the community
    to review and update the answers. The latest version of the complete
    perlfaq is at http://faq.perl.org .

    --------------------------------------------------------------------

    8.37: How do I find out if I'm running interactively or not?

    (contributed by brian d foy)

    This is a difficult question to answer, and the best answer is only a
    guess.

    What do you really want to know? If you merely want to know if one of
    your filehandles is connected to a terminal, you can try the "-t" file
    test:

    if( -t STDOUT ) {
    print "I'm connected to a terminal!\n";
    }

    However, you might be out of luck if you expect that means there is a
    real person on the other side. With the "Expect" module, another program
    can pretend to be a person. The program might even come close to passing
    the Turing test.

    The "IO::Interactive" module does the best it can to give you an answer.
    Its "is_interactive" function returns an output filehandle; that
    filehandle points to standard output if the module thinks the session is
    interactive. Otherwise, the filehandle is a null handle that simply
    discards the output:

    use IO::Interactive;

    print { is_interactive } "I might go to standard output!\n";

    This still doesn't guarantee that a real person is answering your
    prompts or reading your output.

    If you want to know how to handle automated testing for your
    distribution, you can check the environment. The CPAN Testers, for
    instance, set the value of "AUTOMATED_TESTING":

    unless( $ENV{AUTOMATED_TESTING} ) {
    print "Hello interactive tester!\n";
    }



    --------------------------------------------------------------------

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    PerlFAQ Server, Feb 19, 2011
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