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).
There really aren't many cohesive "versions" of this ‒ indeed, so long
as grantpt(3) exists it behaves precisely as described here ‒
inasmuch as different systems, historically, had different ptys,
and thus different implementations. These are all but trivia.
Cc: Jakub Wilk <jwilk@xxxxxxxxx>
Signed-off-by: Ahelenia Ziemiańska <nabijaczleweli@xxxxxxxxxxxxxxxxxx>
---
I originally thought to do so, but decided against it because I'm not
substantially changing this paragraph and it's already in VERSIONS...
Moved with rationale added.
Also, administriva-wise, git pull tells me
[PATCH 1/2] statfs.2: unshade as deprecated, but direct to statvfs(3)
with msgid
<b4b871ffdf8f764ffd6c25039f3944b08748bd3e.1687553930.git.nabijaczleweli@xxxxxxxxxxxxxxxxxx>
is the last outstanding patch I have rn, sans this one.
man3/grantpt.3 | 22 ++++++++++------------
1 file changed, 10 insertions(+), 12 deletions(-)
diff --git a/man3/grantpt.3 b/man3/grantpt.3
index a19172a3e..949f70de9 100644
--- a/man3/grantpt.3
+++ b/man3/grantpt.3
@@ -83,18 +83,6 @@ .SH ATTRIBUTES
.hy
.ad
.sp 1
-.SH VERSIONS
-Many systems implement 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).
.SH STANDARDS
POSIX.1-2008.
.SH HISTORY
@@ -103,6 +91,16 @@ .SH HISTORY
.PP
This is part of the UNIX 98 pseudoterminal support, see
.BR pts (4).
+.PP
+Historical systems implemented this function via a set-user-ID helper binary
+called "pt_chown".
+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 SEE ALSO
.BR open (2),
.BR posix_openpt (3),
--
2.39.2
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