exec: add support for Plan 9

R=paulzhol, mirtchovski, fshahriar, alex.brainman, r
CC=golang-dev
https://golang.org/cl/4386041

2 files changed, 54 insertions, 0 deletions

diff --git a/src/pkg/exec/Makefile b/src/pkg/exec/Makefile
index 262ecac85e..90bb74b41c 100644
--- a/src/pkg/exec/Makefile
+++ b/src/pkg/exec/Makefile
@@ -20,6 +20,9 @@ GOFILES_linux=\
 GOFILES_windows=\
 	lp_windows.go\
 
+GOFILES_plan9=\
+	lp_plan9.go\
+
 GOFILES+=$(GOFILES_$(GOOS))
 
 include ../../Make.pkg
diff --git a/src/pkg/exec/lp_plan9.go b/src/pkg/exec/lp_plan9.go
new file mode 100644
index 0000000000..d0912f9e9e
--- /dev/null
+++ b/src/pkg/exec/lp_plan9.go
@@ -0,0 +1,51 @@
+// 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 (
+	"os"
+	"strings"
+)
+
+// ErrNotFound is the error resulting if a path search failed to find an executable file.
+var ErrNotFound = os.ErrorString("executable file not found in $path")
+
+func findExecutable(file string) os.Error {
+	d, err := os.Stat(file)
+	if err != nil {
+		return err
+	}
+	if d.IsRegular() && d.Permission()&0111 != 0 {
+		return nil
+	}
+	return os.EPERM
+}
+
+// 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.
+func LookPath(file string) (string, os.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", -1) {
+		if err := findExecutable(dir + "/" + file); err == nil {
+			return dir + "/" + file, nil
+		}
+	}
+	return "", &Error{file, ErrNotFound}
+}