fish-shell/sphinx_doc_src/cmds/isatty.rst

isatty - test if a file descriptor is a tty.
==========================================

Synopsis
--------

isatty [FILE DESCRIPTOR]


Description
------------

`isatty` tests if a file descriptor is a tty.

`FILE DESCRIPTOR` may be either the number of a file descriptor, or one of the strings `stdin`, `stdout`, or `stderr`.

If the specified file descriptor is a tty, 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:

\fish
isatty
isatty stdout
isatty 2
echo | isatty 1
\endfish

And these will exit non-zero:

\fish
echo | isatty
isatty 9
isatty stdout > file
isatty 2 2> file
\endfish
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			`==========================================`

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			`--------`
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			`isatty [FILE DESCRIPTOR]`
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			`------------`
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			`isatty` tests if a file descriptor is a tty.

			`FILE DESCRIPTOR` may be either the number of a file descriptor, or one of the strings `stdin`, `stdout`, or `stderr`.

			`If the specified file descriptor is a tty, the exit status of the command is zero. Otherwise, the exit status is non-zero. No messages are printed to standard error.`


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

			`\fish`
			`isatty`
			`isatty stdout`
			`isatty 2`
			`echo \| isatty 1`
			`\endfish`

			`And these will exit non-zero:`

			`\fish`
			`echo \| isatty`
			`isatty 9`
			`isatty stdout > file`
			`isatty 2 2> file`
			`\endfish`