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60808a4820
Presently, `isatty` only works on a handful of keywords. Here it is rewritten to be able to take any path, device or fd number as an argument, and eliminates errors printed to stdout. Per discussion in #1228, using `builtin test -c` within a pipe to test special file descriptors is not viable, so this implementation specifcially uses `command test`. Additionally, a note has been added to the documentation of `test` regarding this potential aberration from the expected output of the test utility under the 'Standards' section.
29 lines
854 B
Text
29 lines
854 B
Text
\section isatty isatty - test if a file or file descriptor is a tty.
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\subsection isatty-synopsis Synopsis
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<tt>isatty [FILE | DEVICE | FILE DESCRIPTOR NUMBER]</tt>
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\subsection isatty-description Description
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<tt>isatty</tt> tests if a file or file descriptor is a tty.
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The argument may be in the form of a file path, device, or file descriptor
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number. Without an argument, <tt>standard input</tt> is implied.
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If the resolved file descriptor is a tty, the command returns zero. Otherwise, the command exits one. No messages are printed to standard error.
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\subsection isatty-examples Examples
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From an interactive shell, the commands below exit with a return value of zero:
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<pre>
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isatty
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isatty stdout
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isatty 2
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echo | isatty /dev/fd/1
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</pre>
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And these will exit non-zero:
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<pre>
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echo | isatty
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isatty /dev/fd/9
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isatty stdout > file
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isatty 2 2> file
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</pre>
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