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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 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 super-user.
.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 .