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35 lines
817 B
Text
35 lines
817 B
Text
\section isatty isatty - test if a file descriptor is a tty.
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\subsection isatty-synopsis Synopsis
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\fish{synopsis}
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isatty [FILE DESCRIPTOR]
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\endfish
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\subsection isatty-description Description
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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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\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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\fish
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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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\endfish
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And these will exit non-zero:
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\fish
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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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\endfish
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