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.Dd June 4, 1993
.Dt INITGROUPS 3
.Os
.Sh NAME
.Nm initgroups
.Nd initialize supplementary group IDs
.Sh SYNOPSIS
.Fd #include <unistd.h>
.Ft int
.Fn initgroups "const char *name" "gid_t basegid"
.Sh DESCRIPTION
The
.Fn initgroups
function uses the
.Xr getgrouplist 3
function to calculate the supplementary group IDs for the user specified in
.Fa name .
This group list is then set up for the current process using
.Xr setgroups 2 .
The
.Fa basegid
is automatically included in the group list.
Typically this value is given as the group number from the password file.
.Pp
If the groups database lists more than
.Ev NGROUPS
groups for
.Fa name
(including one for
.Fa basegid ) ,
the later groups are ignored.
.Sh RETURN VALUES
The
.Fn initgroups
function returns \-1 if it was not invoked by the superuser.
.Sh SEE ALSO
.Xr setgroups 2 ,
.Xr getgrouplist 3
.Sh HISTORY
The
.Fn initgroups
function appeared in
.Bx 4.2 .
.Sh BUGS
The
.Xr getgrouplist 3
function called by
.Fn initgroups
uses the routines based on
.Xr getgrent 3 .
If the invoking program uses any of these routines, the group structure
will be overwritten in the call to
.Fn initgroups .