posix_spawn_file_actions_adddup2(3): Document difference with dup2().

The ability to clear a file descriptor's close-on-exec flag via
posix_spawn_file_actions_adddup2() is in fact proposed in Austin Group issue
#411.

MFC after:	1 week
This commit is contained in:
Jilles Tjoelker 2013-05-09 21:29:13 +00:00
parent 08eaffd830
commit 38cf77de66
Notes: svn2git 2020-12-20 02:59:44 +00:00
svn path=/head/; revision=250421

View File

@ -123,7 +123,19 @@ to be duplicated as
dup2(fildes, newfildes)
.Ed
.Pp
had been called) when a new process is spawned using this file actions object.
had been called) when a new process is spawned using this file actions object,
except that the
.Dv FD_CLOEXEC
flag for
.Fa newfildes
is cleared even if
.Fa fildes
is equal to
.Fa newfildes .
The difference from
.Fn dup2
is useful for passing a particular file descriptor
to a particular child process.
.Pp
The
.Fn posix_spawn_file_actions_addclose
@ -169,7 +181,16 @@ The
and
.Fn posix_spawn_file_actions_addclose
functions conform to
.St -p1003.1-2001 .
.St -p1003.1-2001 ,
with the exception of the behavior of
.Fn posix_spawn_file_actions_adddup2
if
.Fa fildes
is equal to
.Fa newfildes
(clearing
.Dv FD_CLOEXEC ) .
A future update of the Standard is expected to require this behavior,
.Sh HISTORY
The
.Fn posix_spawn_file_actions_addopen ,