1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
|
// Copyright 2010 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.
// General environment variables.
package os
import (
"internal/testlog"
"syscall"
)
// Expand replaces ${var} or $var in the string based on the mapping function.
// For example, os.ExpandEnv(s) is equivalent to os.Expand(s, os.Getenv).
func Expand(s string, mapping func(string) string) string {
var buf []byte
// ${} is all ASCII, so bytes are fine for this operation.
i := 0
for j := 0; j < len(s); j++ {
if s[j] == '$' && j+1 < len(s) {
if buf == nil {
buf = make([]byte, 0, 2*len(s))
}
buf = append(buf, s[i:j]...)
name, w := getShellName(s[j+1:])
if name == "" && w > 0 {
// Encountered invalid syntax; eat the
// characters.
} else if name == "" {
// Valid syntax, but $ was not followed by a
// name. Leave the dollar character untouched.
buf = append(buf, s[j])
} else {
buf = append(buf, mapping(name)...)
}
j += w
i = j + 1
}
}
if buf == nil {
return s
}
return string(buf) + s[i:]
}
// ExpandEnv replaces ${var} or $var in the string according to the values
// of the current environment variables. References to undefined
// variables are replaced by the empty string.
func ExpandEnv(s string) string {
return Expand(s, Getenv)
}
// isShellSpecialVar reports whether the character identifies a special
// shell variable such as $*.
func isShellSpecialVar(c uint8) bool {
switch c {
case '*', '#', '$', '@', '!', '?', '-', '0', '1', '2', '3', '4', '5', '6', '7', '8', '9':
return true
}
return false
}
// isAlphaNum reports whether the byte is an ASCII letter, number, or underscore.
func isAlphaNum(c uint8) bool {
return c == '_' || '0' <= c && c <= '9' || 'a' <= c && c <= 'z' || 'A' <= c && c <= 'Z'
}
// getShellName returns the name that begins the string and the number of bytes
// consumed to extract it. If the name is enclosed in {}, it's part of a ${}
// expansion and two more bytes are needed than the length of the name.
func getShellName(s string) (string, int) {
switch {
case s[0] == '{':
if len(s) > 2 && isShellSpecialVar(s[1]) && s[2] == '}' {
return s[1:2], 3
}
// Scan to closing brace
for i := 1; i < len(s); i++ {
if s[i] == '}' {
if i == 1 {
return "", 2 // Bad syntax; eat "${}"
}
return s[1:i], i + 1
}
}
return "", 1 // Bad syntax; eat "${"
case isShellSpecialVar(s[0]):
return s[0:1], 1
}
// Scan alphanumerics.
var i int
for i = 0; i < len(s) && isAlphaNum(s[i]); i++ {
}
return s[:i], i
}
// Getenv retrieves the value of the environment variable named by the key.
// It returns the value, which will be empty if the variable is not present.
// To distinguish between an empty value and an unset value, use LookupEnv.
func Getenv(key string) string {
testlog.Getenv(key)
v, _ := syscall.Getenv(key)
return v
}
// LookupEnv retrieves the value of the environment variable named
// by the key. If the variable is present in the environment the
// value (which may be empty) is returned and the boolean is true.
// Otherwise the returned value will be empty and the boolean will
// be false.
func LookupEnv(key string) (string, bool) {
testlog.Getenv(key)
return syscall.Getenv(key)
}
// Setenv sets the value of the environment variable named by the key.
// It returns an error, if any.
func Setenv(key, value string) error {
err := syscall.Setenv(key, value)
if err != nil {
return NewSyscallError("setenv", err)
}
return nil
}
// Unsetenv unsets a single environment variable.
func Unsetenv(key string) error {
return syscall.Unsetenv(key)
}
// Clearenv deletes all environment variables.
func Clearenv() {
syscall.Clearenv()
}
// Environ returns a copy of strings representing the environment,
// in the form "key=value".
func Environ() []string {
return syscall.Environ()
}
|
