1 files changed, 53 insertions, 0 deletions
diff --git a/src/os/exec/lp_plan9.go b/src/os/exec/lp_plan9.go
new file mode 100644
index 000000000..5aa8a54ed
--- /dev/null
+++ b/src/os/exec/lp_plan9.go
@@ -0,0 +1,53 @@
+// 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.
+
+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 findExecutable(file string) error {
+	d, err := os.Stat(file)
+	if err != nil {
+		return err
+	}
+	if m := d.Mode(); !m.IsDir() && m&0111 != 0 {
+		return nil
+	}
+	return os.ErrPermission
+}
+
+// LookPath searches for an executable binary named file
+// in the directories named by the path environment variable.
+// If file begins with "/", "#", "./", or "../", it is tried
+// directly and the path is not consulted.
+// The result may be an absolute path or a path relative to the current directory.
+func LookPath(file string) (string, error) {
+	// skip the path lookup for these prefixes
+	skip := []string{"/", "#", "./", "../"}
+
+	for _, p := range skip {
+		if strings.HasPrefix(file, p) {
+			err := findExecutable(file)
+			if err == nil {
+				return file, nil
+			}
+			return "", &Error{file, err}
+		}
+	}
+
+	path := os.Getenv("path")
+	for _, dir := range strings.Split(path, "\000") {
+		if err := findExecutable(dir + "/" + file); err == nil {
+			return dir + "/" + file, nil
+		}
+	}
+	return "", &Error{file, ErrNotFound}
+}