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46 lines
792 B
ReStructuredText
46 lines
792 B
ReStructuredText
isatty - test if a file descriptor is a tty.
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============================================
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Synopsis
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--------
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isatty [FILE DESCRIPTOR]
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Description
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-----------
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``isatty`` tests if a file descriptor is a tty.
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``FILE DESCRIPTOR`` may be either the number of a file descriptor, or one of the strings ``stdin``, ``stdout``, or ``stderr``.
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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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Examples
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--------
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From an interactive shell, the commands below exit with a return value of zero:
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::
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isatty
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isatty stdout
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isatty 2
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echo | isatty 1
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And these will exit non-zero:
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::
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echo | isatty
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isatty 9
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isatty stdout > file
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isatty 2 2> file
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