exec.LookPath() unix/windows separation
R=brainman, rsc, vcc, rsc1
CC=golang-dev
https://golang.org/cl/2068041
diff --git a/src/pkg/exec/lp_unix.go b/src/pkg/exec/lp_unix.go
new file mode 100644
index 0000000..10f3da1
--- /dev/null
+++ b/src/pkg/exec/lp_unix.go
@@ -0,0 +1,45 @@
+// 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 (
+ "os"
+ "strings"
+)
+
+func canExec(file string) bool {
+ d, err := os.Stat(file)
+ if err != nil {
+ return false
+ }
+ return d.IsRegular() && d.Permission()&0111 != 0
+}
+
+// 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.
+func LookPath(file string) (string, os.Error) {
+ // NOTE(rsc): I wish we could use the Plan 9 behavior here
+ // (only bypass the path if file begins with / or ./ or ../)
+ // but that would not match all the Unix shells.
+
+ if strings.Index(file, "/") >= 0 {
+ if canExec(file) {
+ return file, nil
+ }
+ return "", os.ENOENT
+ }
+ pathenv := os.Getenv("PATH")
+ for _, dir := range strings.Split(pathenv, ":", -1) {
+ if dir == "" {
+ // Unix shell semantics: path element "" means "."
+ dir = "."
+ }
+ if canExec(dir + "/" + file) {
+ return dir + "/" + file, nil
+ }
+ }
+ return "", os.ENOENT
+}
