libgo/go/os/exec/lp_unix.go

   1 // Copyright 2010 The Go Authors.  All rights reserved.
   2 // Use of this source code is governed by a BSD-style
   3 // license that can be found in the LICENSE file.
   4
   5 // +build darwin freebsd linux netbsd openbsd
   6
   7 package exec
   8
   9 import (
  10         "errors"
  11         "os"
  12         "strings"
  13 )
  14
  15 // ErrNotFound is the error resulting if a path search failed to find an executable file.
  16 var ErrNotFound = errors.New("executable file not found in $PATH")
  17
  18 func findExecutable(file string) error {
  19         d, err := os.Stat(file)
  20         if err != nil {
  21                 return err
  22         }
  23         if m := d.Mode(); !m.IsDir() && m&0111 != 0 {
  24                 return nil
  25         }
  26         return os.ErrPermission
  27 }
  28
  29 // LookPath searches for an executable binary named file
  30 // in the directories named by the PATH environment variable.
  31 // If file contains a slash, it is tried directly and the PATH is not consulted.
  32 func LookPath(file string) (string, error) {
  33         // NOTE(rsc): I wish we could use the Plan 9 behavior here
  34         // (only bypass the path if file begins with / or ./ or ../)
  35         // but that would not match all the Unix shells.
  36
  37         if strings.Contains(file, "/") {
  38                 err := findExecutable(file)
  39                 if err == nil {
  40                         return file, nil
  41                 }
  42                 return "", &Error{file, err}
  43         }
  44         pathenv := os.Getenv("PATH")
  45         if pathenv == "" {
  46                 return "", &Error{file, ErrNotFound}
  47         }
  48         for _, dir := range strings.Split(pathenv, ":") {
  49                 if dir == "" {
  50                         // Unix shell semantics: path element "" means "."
  51                         dir = "."
  52                 }
  53                 path := dir + "/" + file
  54                 if err := findExecutable(path); err == nil {
  55                         return path, nil
  56                 }
  57         }
  58         return "", &Error{file, ErrNotFound}
  59 }