150 lines
2.8 KiB
Go
150 lines
2.8 KiB
Go
// Copyright 2010 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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// +build darwin dragonfly freebsd linux nacl netbsd openbsd solaris
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// Unix environment variables.
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package syscall
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import "sync"
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var (
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// envOnce guards initialization by copyenv, which populates env.
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envOnce sync.Once
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// envLock guards env and envs.
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envLock sync.RWMutex
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// env maps from an environment variable to its first occurrence in envs.
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env map[string]int
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// envs is provided by the runtime. elements are expected to
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// be of the form "key=value". An empty string means deleted
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// (or a duplicate to be ignored).
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envs []string = runtime_envs()
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)
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func runtime_envs() []string // in package runtime
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// setenv_c and unsetenv_c are provided by the runtime but are no-ops
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// if cgo isn't loaded.
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func setenv_c(k, v string)
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func unsetenv_c(k string)
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func copyenv() {
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env = make(map[string]int)
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for i, s := range envs {
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for j := 0; j < len(s); j++ {
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if s[j] == '=' {
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key := s[:j]
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if _, ok := env[key]; !ok {
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env[key] = i // first mention of key
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} else {
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// Clear duplicate keys. This permits Unsetenv to
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// safely delete only the first item without
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// worrying about unshadowing a later one,
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// which might be a security problem.
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envs[i] = ""
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}
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break
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}
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}
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}
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}
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func Unsetenv(key string) error {
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envOnce.Do(copyenv)
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envLock.Lock()
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defer envLock.Unlock()
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if i, ok := env[key]; ok {
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envs[i] = ""
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delete(env, key)
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}
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unsetenv_c(key)
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return nil
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}
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func Getenv(key string) (value string, found bool) {
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envOnce.Do(copyenv)
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if len(key) == 0 {
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return "", false
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}
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envLock.RLock()
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defer envLock.RUnlock()
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i, ok := env[key]
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if !ok {
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return "", false
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}
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s := envs[i]
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for i := 0; i < len(s); i++ {
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if s[i] == '=' {
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return s[i+1:], true
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}
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}
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return "", false
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}
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func Setenv(key, value string) error {
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envOnce.Do(copyenv)
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if len(key) == 0 {
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return EINVAL
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}
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for i := 0; i < len(key); i++ {
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if key[i] == '=' || key[i] == 0 {
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return EINVAL
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}
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}
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for i := 0; i < len(value); i++ {
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if value[i] == 0 {
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return EINVAL
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}
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}
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envLock.Lock()
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defer envLock.Unlock()
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i, ok := env[key]
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kv := key + "=" + value
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if ok {
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envs[i] = kv
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} else {
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i = len(envs)
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envs = append(envs, kv)
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}
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env[key] = i
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setenv_c(key, value)
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return nil
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}
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func Clearenv() {
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envOnce.Do(copyenv) // prevent copyenv in Getenv/Setenv
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envLock.Lock()
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defer envLock.Unlock()
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for k := range env {
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unsetenv_c(k)
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}
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env = make(map[string]int)
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envs = []string{}
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}
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func Environ() []string {
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envOnce.Do(copyenv)
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envLock.RLock()
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defer envLock.RUnlock()
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a := make([]string, 0, len(envs))
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for _, env := range envs {
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if env != "" {
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a = append(a, env)
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}
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}
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return a
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}
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