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// Copyright 2011 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.
// Plan 9 environment variables.
package syscall
import (
"errors"
"sync"
)
var (
// envOnce guards initialization by copyenv, which populates env.
envOnce sync.Once
// envLock guards env.
envLock sync.RWMutex
// env maps from an environment variable to its value.
env map[string]string
)
func readenv(key string) (string, error) {
fd, err := Open("/env/"+key, O_RDONLY)
if err != nil {
return "", err
}
defer Close(fd)
l, _ := Seek(fd, 0, 2)
Seek(fd, 0, 0)
buf := make([]byte, l)
n, err := Read(fd, buf)
if err != nil {
return "", err
}
if n > 0 && buf[n-1] == 0 {
buf = buf[:n-1]
}
return string(buf), nil
}
func writeenv(key, value string) error {
fd, err := Create("/env/"+key, O_RDWR, 0666)
if err != nil {
return err
}
defer Close(fd)
_, err = Write(fd, []byte(value))
return err
}
func copyenv() {
env = make(map[string]string)
fd, err := Open("/env", O_RDONLY)
if err != nil {
return
}
defer Close(fd)
files, err := readdirnames(fd)
if err != nil {
return
}
for _, key := range files {
v, err := readenv(key)
if err != nil {
continue
}
env[key] = v
}
}
func Getenv(key string) (value string, found bool) {
envOnce.Do(copyenv)
if len(key) == 0 {
return "", false
}
envLock.RLock()
defer envLock.RUnlock()
v, ok := env[key]
if !ok {
return "", false
}
return v, true
}
func Setenv(key, value string) error {
envOnce.Do(copyenv)
if len(key) == 0 {
return errors.New("zero length key")
}
envLock.Lock()
defer envLock.Unlock()
err := writeenv(key, value)
if err != nil {
return err
}
env[key] = value
return nil
}
func Clearenv() {
envOnce.Do(copyenv) // prevent copyenv in Getenv/Setenv
envLock.Lock()
defer envLock.Unlock()
env = make(map[string]string)
RawSyscall(SYS_RFORK, RFCENVG, 0, 0)
}
func Environ() []string {
envOnce.Do(copyenv)
envLock.RLock()
defer envLock.RUnlock()
a := make([]string, len(env))
i := 0
for k, v := range env {
a[i] = k + "=" + v
i++
}
return a
}
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