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fcntl.2: Describe how to check whether the kernel supports a particular command
Reported-by: Jeff Layton <jlayton@poochiereds.net> Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
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man2/fcntl.2
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man2/fcntl.2
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@ -89,6 +89,17 @@ and we identify the argument using the name
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or
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.I void
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is specified if the argument is not required.
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Certain of the operations below are supported only since a particular
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Linux kernel version.
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The preferred method of checking whether the host kernel supports
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a particular operation is to invoke
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.BR fcntl ()
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with the desired
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.IR cmd
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value and then test whether the call failed with
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.BR EINVAL ,
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indicating that the kernel does not recognize this value.
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.SS Duplicating a file descriptor
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.TP
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.BR F_DUPFD " (\fIint\fP)"
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