unix.7: Enhance the description of SCM_RIGHTS

The existing description is rather thin. More can be said.

Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>

diff --git a/man7/unix.7 b/man7/unix.7
index 46b1914b843e64f1f41db77349d37c09c44b1921..0850ebc1be48d5e4e284537034efcbf28337868f 100644 (file)
--- a/man7/unix.7
+++ b/man7/unix.7
@@ -369,8 +369,16 @@ For more information see
 .B SCM_RIGHTS
 Send or receive a set of open file descriptors from another process.
 The data portion contains an integer array of the file descriptors.
-The passed file descriptors behave as though they have been created with
-.BR dup (2).
+Commonly, this operation is referred to as "passing a file descriptor"
+to another process.
+However, more accurately,
+what is being passed is a reference to an open file description (see
+.BR open (2)),
+and in the receiving process it is likely that a different
+file descriptor number will be used.
+Semantically, this operation is equivalent to duplicating
+.RB ( dup (2))
+a file descriptor into the file descriptor table of another process.
 .IP
 The kernel constant
 .BR SCM_MAX_FD