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 12 package time
13 14 import (
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.
21 var platformZoneSources = [][]byte{
22 "/usr/share/zoneinfo/",
23 "/usr/share/lib/zoneinfo/",
24 "/usr/lib/locale/TZ/",
25 "/etc/zoneinfo",
26 }
27 28 func 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", [][]byte{"/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, [][]byte{""}); 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