github.com/mattn/go@v0.0.0-20171011075504-07f7db3ea99f/src/time/zoneinfo_unix.go (about)

     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  // +build darwin,386 darwin,amd64 dragonfly freebsd linux,!android nacl netbsd openbsd solaris
     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), http://en.wikipedia.org/wiki/Zoneinfo,
    10  // and ftp://munnari.oz.au/pub/oldtz/
    11  
    12  package time
    13  
    14  import (
    15  	"runtime"
    16  	"syscall"
    17  )
    18  
    19  // Many systems use /usr/share/zoneinfo, Solaris 2 has
    20  // /usr/share/lib/zoneinfo, IRIX 6 has /usr/lib/locale/TZ.
    21  var zoneSources = []string{
    22  	"/usr/share/zoneinfo/",
    23  	"/usr/share/lib/zoneinfo/",
    24  	"/usr/lib/locale/TZ/",
    25  	runtime.GOROOT() + "/lib/time/zoneinfo.zip",
    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" means use /usr/share/zoneinfo/foo.
    33  
    34  	tz, ok := syscall.Getenv("TZ")
    35  	switch {
    36  	case !ok:
    37  		z, err := loadLocation("localtime", []string{"/etc/"})
    38  		if err == nil {
    39  			localLoc = *z
    40  			localLoc.name = "Local"
    41  			return
    42  		}
    43  	case tz != "" && tz != "UTC":
    44  		if z, err := loadLocation(tz, zoneSources); err == nil {
    45  			localLoc = *z
    46  			return
    47  		}
    48  	}
    49  
    50  	// Fall back to UTC.
    51  	localLoc.name = "UTC"
    52  }