libgo/go/os/exec/lp_plan9.go

   1 // Copyright 2011 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 package exec
   6
   7 import (
   8         "errors"
   9         "os"
  10         "path/filepath"
  11         "strings"
  12 )
  13
  14 // ErrNotFound is the error resulting if a path search failed to find an executable file.
  15 var ErrNotFound = errors.New("executable file not found in $path")
  16
  17 func findExecutable(file string) error {
  18         d, err := os.Stat(file)
  19         if err != nil {
  20                 return err
  21         }
  22         if m := d.Mode(); !m.IsDir() && m&0111 != 0 {
  23                 return nil
  24         }
  25         return os.ErrPermission
  26 }
  27
  28 // LookPath searches for an executable binary named file
  29 // in the directories named by the path environment variable.
  30 // If file begins with "/", "#", "./", or "../", it is tried
  31 // 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         // skip the path lookup for these prefixes
  35         skip := []string{"/", "#", "./", "../"}
  36
  37         for _, p := range skip {
  38                 if strings.HasPrefix(file, p) {
  39                         err := findExecutable(file)
  40                         if err == nil {
  41                                 return file, nil
  42                         }
  43                         return "", &Error{file, err}
  44                 }
  45         }
  46
  47         path := os.Getenv("path")
  48         for _, dir := range filepath.SplitList(path) {
  49                 path := filepath.Join(dir, file)
  50                 if err := findExecutable(path); err == nil {
  51                         return path, nil
  52                 }
  53         }
  54         return "", &Error{file, ErrNotFound}
  55 }