docs/isatty: Mention default value for FILE DESCRIPTOR

As seen in share/functions/isatty.fish (note the empty string):

    switch "$argv"
        case stdin ''
            set fd 0
This commit is contained in:
Aurelio Jargas 2020-09-05 07:24:39 +02:00 committed by Fabian Homborg
parent 55bc6a27c6
commit d4fe110f23

View File

@ -15,7 +15,7 @@ Description
``isatty`` tests if a file descriptor is a terminal (as opposed to a file). The name is derived from the system call of the same name, which for historical reasons refers to a teletypewriter (TTY).
``FILE DESCRIPTOR`` may be either the number of a file descriptor, or one of the strings ``stdin``, ``stdout``, or ``stderr``.
``FILE DESCRIPTOR`` may be either the number of a file descriptor, or one of the strings ``stdin``, ``stdout``, or ``stderr``. If not specified, zero is assumed.
If the specified file descriptor is a terminal device, the exit status of the command is zero. Otherwise, the exit status is non-zero. No messages are printed to standard error.