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freebsd/lib/libc/sys/setgroups.2
Brooks Davis 54404cfb13 In preparation for raising NGROUPS and NGROUPS_MAX, change base
system callers of getgroups(), getgrouplist(), and setgroups() to
allocate buffers dynamically.  Specifically, allocate a buffer of size
sysconf(_SC_NGROUPS_MAX)+1 (+2 in a few cases to allow for overflow).

This (or similar gymnastics) is required for the code to actually follow
the POSIX.1-2008 specification where {NGROUPS_MAX} may differ at runtime
and where getgroups may return {NGROUPS_MAX}+1 results on systems like
FreeBSD which include the primary group.

In id(1), don't pointlessly add the primary group to the list of all
groups, it is always the first result from getgroups().  In principle
the old code was more portable, but this was only done in one of the two
places where getgroups() was called to the overall effect was pointless.

Document the actual POSIX requirements in the getgroups(2) and
setgroups(2) manpages.  We do not yet support a dynamic NGROUPS, but we
may in the future.

MFC after:	2 weeks
2009-06-19 15:58:24 +00:00

88 lines
2.6 KiB
Groff

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.\" @(#)setgroups.2 8.2 (Berkeley) 4/16/94
.\" $FreeBSD$
.\"
.Dd April 16, 1994
.Dt SETGROUPS 2
.Os
.Sh NAME
.Nm setgroups
.Nd set group access list
.Sh LIBRARY
.Lb libc
.Sh SYNOPSIS
.In sys/param.h
.In unistd.h
.Ft int
.Fn setgroups "int ngroups" "const gid_t *gidset"
.Sh DESCRIPTION
The
.Fn setgroups
system call
sets the group access list of the current user process
according to the array
.Fa gidset .
The
.Fa ngroups
argument
indicates the number of entries in the array and must be no
more than
.Dv {NGROUPS_MAX}+1 .
.Pp
Only the super-user may set a new group list.
.Sh RETURN VALUES
.Rv -std setgroups
.Sh ERRORS
The
.Fn setgroups
system call will fail if:
.Bl -tag -width Er
.It Bq Er EPERM
The caller is not the super-user.
.It Bq Er EINVAL
The number specified in the
.Fa ngroups
argument is larger than the
.Dv {NGROUPS_MAX}+1
limit.
.It Bq Er EFAULT
The address specified for
.Fa gidset
is outside the process
address space.
.El
.Sh SEE ALSO
.Xr getgroups 2 ,
.Xr initgroups 3
.Sh HISTORY
The
.Fn setgroups
system call appeared in
.Bx 4.2 .