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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 copyenv, which populates env.
envOnce sync.Once
// envLock guards env and envs.
envLock sync.RWMutex
// env maps from an environment variable to its value.
env = make(map[string]string)
// envs contains elements of env in the form "key=value".
envs []string
errZeroLengthKey = errors.New("zero length key")
errShortWrite = errors.New("i/o count too small")
)
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)
b := []byte(value)
n, err := Write(fd, b)
if err != nil {
return err
}
if n != len(b) {
return errShortWrite
}
return nil
}
func copyenv() {
fd, err := Open("/env", O_RDONLY)
if err != nil {
return
}
defer Close(fd)
files, err := readdirnames(fd)
if err != nil {
return
}
envs = make([]string, len(files))
i := 0
for _, key := range files {
v, err := readenv(key)
if err != nil {
continue
}
env[key] = v
envs[i] = key + "=" + v
i++
}
}
func Getenv(key string) (value string, found bool) {
if len(key) == 0 {
return "", false
}
envLock.RLock()
defer envLock.RUnlock()
if v, ok := env[key]; ok {
return v, true
}
v, err := readenv(key)
if err != nil {
return "", false
}
env[key] = v
envs = append(envs, key+"="+v)
return v, true
}
func Setenv(key, value string) error {
if len(key) == 0 {
return errZeroLengthKey
}
envLock.Lock()
defer envLock.Unlock()
err := writeenv(key, value)
if err != nil {
return err
}
env[key] = value
envs = append(envs, key+"="+value)
return nil
}
func Clearenv() {
envLock.Lock()
defer envLock.Unlock()
env = make(map[string]string)
envs = []string{}
RawSyscall(SYS_RFORK, RFCENVG, 0, 0)
}
func Environ() []string {
envLock.RLock()
defer envLock.RUnlock()
envOnce.Do(copyenv)
return append([]string(nil), envs...)
}
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