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`
			`================================================`
Switch command docs from \section to reStructuredText 2018-12-17 09:39:33 +08:00
Migrate the 'synopsis' sections to .rst format 2018-12-18 09:58:24 +08:00			`Synopsis`
			`--------`
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docs: update all command synopsis formatting Adds synopses for those commands missing them. Moves all synopsis sections to code blocks. This improves the appearance, although highlighting as fish code may not be the ideal appearance. 2019-09-17 17:59:04 +08:00			`::`
Migrate the 'synopsis' sections to .rst format 2018-12-18 09:58:24 +08:00
docs: update all command synopsis formatting Adds synopses for those commands missing them. Moves all synopsis sections to code blocks. This improves the appearance, although highlighting as fish code may not be the ideal appearance. 2019-09-17 17:59:04 +08:00			`isatty [FILE DESCRIPTOR]`
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Convert \\subsection sections into rst format 2018-12-19 10:44:30 +08:00			`Description`
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
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
			`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
			`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`