FreeBSD, OpenBSD, and Linux (/dev/ptmx) do all intialisation in open(2),
and grantpt(3) is a no-op (that checks whether the fd is a pty, except on
musl).
The illumos gate and NetBSD do a ioctl (and, indeed, illumos-gate commit
facf4a8d7b59fde89a8662b4f4c73a758e6c402c ("PSARC/2003/246 Filesystem
Driven Device Naming"), which kills pt_chmod, notes that it's been
"6464196 bfu should remove pt_chmod, obsoleted by /dev filesystem").
glibc 2.33 completely kills BSD PTY support on Linux
(Debian hasn't configured with them on any architecture since 2007:
https://bugs.debian.org/338404
and even earlier on some arches; they're really just trivia under
Linux ‒ this may be better served stuffed into HISTORY as an explainer
for the SIGCHLD thing, since regardless of the "version", the behaviour
is well-defined and consistent).
Cc: Jakub Wilk <jwilk@xxxxxxxxx>
Signed-off-by: Ahelenia Ziemiańska <nabijaczleweli@xxxxxxxxxxxxxxxxxx>
---
> The illumos gate and NetBSD do a ioctl (and, indeed, illumos-gate commit
paren level 1
v
> facf4a8d7b59fde89a8662b4f4c73a758e6c402c ("PSARC/2003/246 Filesystem
paren level 2
v
> Driven Device Naming"), which kills pt_chmod, notes that it's been
this is an in-line 2-column quote of the commit message
(which I've misindented to 3)
vvv
> 6464196 bfu should remove pt_chmod, obsoleted by /dev filesystem).
So it works by "it doesn't", it's psycho indent, probably related to
Date: Mon Jun 19 02:01:46 2023 +0200
I turned the blockquote into a ""-quote, which should make more sense.
Numberised open() and grantpt().
man3/grantpt.3 | 18 ++++++++----------
1 file changed, 8 insertions(+), 10 deletions(-)
diff --git a/man3/grantpt.3 b/man3/grantpt.3
index a19172a3e..e3d4e4aaa 100644
--- a/man3/grantpt.3
+++ b/man3/grantpt.3
@@ -84,17 +84,15 @@ .SH ATTRIBUTES
.ad
.sp 1
.SH VERSIONS
-Many systems implement this function via a set-user-ID helper binary
+Historical systems implemented this function via a set-user-ID helper binary
called "pt_chown".
-On Linux systems with a devpts filesystem (present since Linux 2.2),
-the kernel normally sets the correct ownership and permissions
-for the pseudoterminal slave when the master is opened
-.RB ( posix_openpt (3)),
-so that nothing must be done by
-.BR grantpt ().
-Thus, no such helper binary is required
-(and indeed it is configured to be absent during the
-glibc build that is typical on many systems).
+glibc on Linux before glibc 2.33 could do so as well,
+in order to support configurations with only BSD pseudoterminals;
+this support has been removed.
+On modern systems this is either a no-op\[em]with
+permissions configured on pty allocation,
+as is the case on Linux\[em]or an
+.BR ioctl (2).
.SH STANDARDS
POSIX.1-2008.
.SH HISTORY
--
2.39.2
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