Update the documentation for setpgrp(2) to reflect the access control

checks that the code actually performs.  Judging from the 4.2BSD
release notes, the docs have only been out of date for 20 years.

PR:	29844

1 files changed, 21 insertions, 7 deletions

diff --git a/lib/libc/sys/setpgid.2 b/lib/libc/sys/setpgid.2
index 37c1d98..c771e03 100644
--- a/lib/libc/sys/setpgid.2
+++ b/lib/libc/sys/setpgid.2
@@ -32,7 +32,7 @@
 .\"     @(#)setpgid.2	8.1 (Berkeley) 6/4/93
 .\" $FreeBSD$
 .\"
-.Dd June 4, 1993
+.Dd February 8, 2004
 .Dt SETPGID 2
 .Os
 .Sh NAME
@@ -59,9 +59,12 @@ If
 .Fa pid
 is zero, then the call applies to the current process.
 .Pp
-If the invoker is not the super-user, then the affected process
-must have the same effective user-id as the invoker or be a descendant
-of the invoking process.
+If the affected process is not the invoking process, then it must be a
+child of the invoking process, it must not have performed an
+.Xr exec 3
+operation, and both processes must be in the same session.
+The requested process group ID must already exist in the session of
+the caller, or it must be equal to the target process ID.
 .Sh RETURN VALUES
 .Rv -std setpgid
 .Sh ERRORS
@@ -70,12 +73,23 @@ The
 system call
 will fail and the process group will not be altered if:
 .Bl -tag -width Er
+.It Bq Er EINVAL
+The requested process group ID is not legal.
 .It Bq Er ESRCH
 The requested process does not exist.
+.It Bq Er ESRCH
+The target process is not the calling process or
+a child of the calling process.
+.It Bq Er EACCES
+The requested process is a child of the calling process,
+but it has performed an
+.Xr exec 3
+operation.
+.It Bq Er EPERM
+The target process is a session leader.
 .It Bq Er EPERM
-The effective user ID of the requested process is different
-from that of the caller and the process is not a descendent
-of the calling process.
+The requested process group ID is not in the session of the caller,
+and it is not equal to the process ID of the target process.
 .El
 .Sh SEE ALSO
 .Xr getpgrp 2