Source file src/os/user/listgroups_unix.go

     1	// Copyright 2016 The Go Authors. All rights reserved.
     2	// Use of this source code is governed by a BSD-style
     3	// license that can be found in the LICENSE file.
     4	
     5	// +build dragonfly darwin freebsd !android,linux netbsd openbsd
     6	// +build cgo,!osusergo
     7	
     8	package user
     9	
    10	import (
    11		"fmt"
    12		"strconv"
    13		"unsafe"
    14	)
    15	
    16	/*
    17	#include <unistd.h>
    18	#include <sys/types.h>
    19	*/
    20	import "C"
    21	
    22	const maxGroups = 2048
    23	
    24	func listGroups(u *User) ([]string, error) {
    25		ug, err := strconv.Atoi(u.Gid)
    26		if err != nil {
    27			return nil, fmt.Errorf("user: list groups for %s: invalid gid %q", u.Username, u.Gid)
    28		}
    29		userGID := C.gid_t(ug)
    30		nameC := make([]byte, len(u.Username)+1)
    31		copy(nameC, u.Username)
    32	
    33		n := C.int(256)
    34		gidsC := make([]C.gid_t, n)
    35		rv := getGroupList((*C.char)(unsafe.Pointer(&nameC[0])), userGID, &gidsC[0], &n)
    36		if rv == -1 {
    37			// Mac is the only Unix that does not set n properly when rv == -1, so
    38			// we need to use different logic for Mac vs. the other OS's.
    39			if err := groupRetry(u.Username, nameC, userGID, &gidsC, &n); err != nil {
    40				return nil, err
    41			}
    42		}
    43		gidsC = gidsC[:n]
    44		gids := make([]string, 0, n)
    45		for _, g := range gidsC[:n] {
    46			gids = append(gids, strconv.Itoa(int(g)))
    47		}
    48		return gids, nil
    49	}
    50	

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