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// 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.
package exec
import (
"errors"
"os"
"strings"
)
// ErrNotFound is the error resulting if a path search failed to find an executable file.
var ErrNotFound = errors.New("executable file not found in %PATH%")
func chkStat(file string) error {
d, err := os.Stat(file)
if err != nil {
return err
}
if d.IsDir() {
return os.ErrPermission
}
return nil
}
func hasExt(file string) bool {
i := strings.LastIndex(file, ".")
if i < 0 {
return false
}
return strings.LastIndexAny(file, `:\/`) < i
}
func findExecutable(file string, exts []string) (string, error) {
if len(exts) == 0 {
return file, chkStat(file)
}
if hasExt(file) {
if chkStat(file) == nil {
return file, nil
}
}
for _, e := range exts {
if f := file + e; chkStat(f) == nil {
return f, nil
}
}
return ``, os.ErrNotExist
}
// LookPath searches for an executable binary named file
// in the directories named by the PATH environment variable.
// If file contains a slash, it is tried directly and the PATH is not consulted.
// LookPath also uses PATHEXT environment variable to match
// a suitable candidate.
// The result may be an absolute path or a path relative to the current directory.
func LookPath(file string) (f string, err error) {
x := os.Getenv(`PATHEXT`)
if x == `` {
x = `.COM;.EXE;.BAT;.CMD`
}
exts := []string{}
for _, e := range strings.Split(strings.ToLower(x), `;`) {
if e == "" {
continue
}
if e[0] != '.' {
e = "." + e
}
exts = append(exts, e)
}
if strings.IndexAny(file, `:\/`) != -1 {
if f, err = findExecutable(file, exts); err == nil {
return
}
return ``, &Error{file, err}
}
if f, err = findExecutable(`.\`+file, exts); err == nil {
return
}
if pathenv := os.Getenv(`PATH`); pathenv != `` {
for _, dir := range splitList(pathenv) {
if f, err = findExecutable(dir+`\`+file, exts); err == nil {
return
}
}
}
return ``, &Error{file, ErrNotFound}
}
func splitList(path string) []string {
// The same implementation is used in SplitList in path/filepath;
// consider changing path/filepath when changing this.
if path == "" {
return []string{}
}
// Split path, respecting but preserving quotes.
list := []string{}
start := 0
quo := false
for i := 0; i < len(path); i++ {
switch c := path[i]; {
case c == '"':
quo = !quo
case c == os.PathListSeparator && !quo:
list = append(list, path[start:i])
start = i + 1
}
}
list = append(list, path[start:])
// Remove quotes.
for i, s := range list {
if strings.Contains(s, `"`) {
list[i] = strings.Replace(s, `"`, ``, -1)
}
}
return list
}
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