fish-shell/doc_src/cmds/isatty.rst

.. _cmd-isatty:

isatty - test if a file descriptor is a terminal
================================================

Synopsis
--------

``isatty`` [*FILE DESCRIPTOR*]

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``. 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.


Examples
--------

From an interactive shell, the commands below exit with a return value of zero::

    isatty
    isatty stdout
    isatty 2
    echo | isatty 1


And these will exit non-zero::

    echo | isatty
    isatty 9
    isatty stdout > file
    isatty 2 2> file
docs: Add labels to all commands This allows us to use :ref: references, which don't require hardcoding it as html [ci skip] 2019-03-31 17:05:09 +08:00			`.. _cmd-isatty:`

docs: update isatty documentation to refer to terminals Use language that is more accurate, similar to what glibc uses. Closes #6355. 2019-11-26 18:18:16 +08:00			`isatty - test if a file descriptor is a terminal`
			`================================================`
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Migrate the 'synopsis' sections to .rst format 2018-12-18 09:58:24 +08:00			`Synopsis`
			`--------`
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Update synopsis of a few stragglers. 2021-12-25 08:15:40 +08:00			``isatty`` [FILE DESCRIPTOR]
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Fix command section separator line lengths 2019-01-03 12:10:47 +08:00			`-----------`
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docs: update isatty documentation to refer to terminals Use language that is more accurate, similar to what glibc uses. Closes #6355. 2019-11-26 18:18:16 +08:00			``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).
Copy doc_src to sphinx_doc_src and add a TOC 2018-12-17 05:08:41 +08:00
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 2020-09-05 13:24:39 +08:00			``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.
Copy doc_src to sphinx_doc_src and add a TOC 2018-12-17 05:08:41 +08:00
docs: update isatty documentation to refer to terminals Use language that is more accurate, similar to what glibc uses. Closes #6355. 2019-11-26 18:18:16 +08:00			`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.`
Copy doc_src to sphinx_doc_src and add a TOC 2018-12-17 05:08:41 +08:00

Convert \\subsection sections into rst format 2018-12-19 10:44:30 +08:00			`Examples`
Fix command section separator line lengths 2019-01-03 12:10:47 +08:00			`--------`
Copy doc_src to sphinx_doc_src and add a TOC 2018-12-17 05:08:41 +08:00
Update synopsis of a few stragglers. 2021-12-25 08:15:40 +08:00			`From an interactive shell, the commands below exit with a return value of zero::`
Switch \fish sections to rst format 2018-12-19 11:14:04 +08:00
			`isatty`
			`isatty stdout`
			`isatty 2`
			`echo \| isatty 1`

Copy doc_src to sphinx_doc_src and add a TOC 2018-12-17 05:08:41 +08:00
Update synopsis of a few stragglers. 2021-12-25 08:15:40 +08:00			`And these will exit non-zero::`
Switch \fish sections to rst format 2018-12-19 11:14:04 +08:00
			`echo \| isatty`
			`isatty 9`
			`isatty stdout > file`
			`isatty 2 2> file`