1 files changed, 49 insertions, 0 deletions
diff --git a/src/os/user/listgroups_unix.go b/src/os/user/listgroups_unix.go
new file mode 100644
index 0000000..70f7af7
--- /dev/null
+++ b/src/os/user/listgroups_unix.go
@@ -0,0 +1,49 @@
+// Copyright 2016 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build dragonfly darwin freebsd !android,linux netbsd openbsd
+// +build cgo,!osusergo
+
+package user
+
+import (
+	"fmt"
+	"strconv"
+	"unsafe"
+)
+
+/*
+#include <unistd.h>
+#include <sys/types.h>
+*/
+import "C"
+
+const maxGroups = 2048
+
+func listGroups(u *User) ([]string, error) {
+	ug, err := strconv.Atoi(u.Gid)
+	if err != nil {
+		return nil, fmt.Errorf("user: list groups for %s: invalid gid %q", u.Username, u.Gid)
+	}
+	userGID := C.gid_t(ug)
+	nameC := make([]byte, len(u.Username)+1)
+	copy(nameC, u.Username)
+
+	n := C.int(256)
+	gidsC := make([]C.gid_t, n)
+	rv := getGroupList((*C.char)(unsafe.Pointer(&nameC[0])), userGID, &gidsC[0], &n)
+	if rv == -1 {
+		// Mac is the only Unix that does not set n properly when rv == -1, so
+		// we need to use different logic for Mac vs. the other OS's.
+		if err := groupRetry(u.Username, nameC, userGID, &gidsC, &n); err != nil {
+			return nil, err
+		}
+	}
+	gidsC = gidsC[:n]
+	gids := make([]string, 0, n)
+	for _, g := range gidsC[:n] {
+		gids = append(gids, strconv.Itoa(int(g)))
+	}
+	return gids, nil
+}