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 dragonfly freebsd linux netbsd openbsd solaris
   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 // The result may be an absolute path or a path relative to the current directory.
  33 func LookPath(file string) (string, error) {
  34         // NOTE(rsc): I wish we could use the Plan 9 behavior here
  35         // (only bypass the path if file begins with / or ./ or ../)
  36         // but that would not match all the Unix shells.
  37
  38         if strings.Contains(file, "/") {
  39                 err := findExecutable(file)
  40                 if err == nil {
  41                         return file, nil
  42                 }
  43                 return "", &Error{file, err}
  44         }
  45         pathenv := os.Getenv("PATH")
  46         if pathenv == "" {
  47                 return "", &Error{file, ErrNotFound}
  48         }
  49         for _, dir := range strings.Split(pathenv, ":") {
  50                 if dir == "" {
  51                         // Unix shell semantics: path element "" means "."
  52                         dir = "."
  53                 }
  54                 path := dir + "/" + file
  55                 if err := findExecutable(path); err == nil {
  56                         return path, nil
  57                 }
  58         }
  59         return "", &Error{file, ErrNotFound}
  60 }