1// Copyright 2009 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//go:build unix && !ios && !android
6
7// Parse "zoneinfo" time zone file.
8// This is a fairly standard file format used on OS X, Linux, BSD, Sun, and others.
9// See tzfile(5), https://en.wikipedia.org/wiki/Zoneinfo,
10// and ftp://munnari.oz.au/pub/oldtz/
11
12package time
13
14import (
15	"syscall"
16)
17
18// Many systems use /usr/share/zoneinfo, Solaris 2 has
19// /usr/share/lib/zoneinfo, IRIX 6 has /usr/lib/locale/TZ,
20// NixOS has /etc/zoneinfo.
21var platformZoneSources = []string{
22	"/usr/share/zoneinfo/",
23	"/usr/share/lib/zoneinfo/",
24	"/usr/lib/locale/TZ/",
25	"/etc/zoneinfo",
26}
27
28func initLocal() {
29	// consult $TZ to find the time zone to use.
30	// no $TZ means use the system default /etc/localtime.
31	// $TZ="" means use UTC.
32	// $TZ="foo" or $TZ=":foo" if foo is an absolute path, then the file pointed
33	// by foo will be used to initialize timezone; otherwise, file
34	// /usr/share/zoneinfo/foo will be used.
35
36	tz, ok := syscall.Getenv("TZ")
37	switch {
38	case !ok:
39		z, err := loadLocation("localtime", []string{"/etc"})
40		if err == nil {
41			localLoc = *z
42			localLoc.name = "Local"
43			return
44		}
45	case tz != "":
46		if tz[0] == ':' {
47			tz = tz[1:]
48		}
49		if tz != "" && tz[0] == '/' {
50			if z, err := loadLocation(tz, []string{""}); err == nil {
51				localLoc = *z
52				if tz == "/etc/localtime" {
53					localLoc.name = "Local"
54				} else {
55					localLoc.name = tz
56				}
57				return
58			}
59		} else if tz != "" && tz != "UTC" {
60			if z, err := loadLocation(tz, platformZoneSources); err == nil {
61				localLoc = *z
62				return
63			}
64		}
65	}
66
67	// Fall back to UTC.
68	localLoc.name = "UTC"
69}
70