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+.\" Copyright (c) 1983, 1991, 1993, 1994
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+.\"
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+.\"
+.Dd January 19, 2018
+.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.
+.Pp
+The first entry of the group array
+.Pq Va gidset[0]
+is used as the effective group-ID for the process.
+This entry is over-written when a setgid program is run.
+To avoid losing access to the privileges of the
+.Va gidset[0]
+entry, it should be duplicated later in the group array.
+By convention,
+this happens because the group value indicated
+in the password file also appears in
+.Pa /etc/group .
+The group value in the password file is placed in
+.Va gidset[0]
+and that value then gets added a second time when the
+.Pa /etc/group
+file is scanned to create the group set.
+.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 .