add os.Getenv()

R=rsc
DELTA=51  (50 added, 0 deleted, 1 changed)
OCL=15665
CL=15667

src/lib/os/Makefile

@@ -3,7 +3,7 @@
 # license that can be found in the LICENSE file.
 
 # DO NOT EDIT.  Automatically generated by gobuild.
-# gobuild -m os os_error.go os_file.go os_time.go
+# gobuild -m os os_error.go os_file.go os_time.go os_env.go
 O=6
 GC=$(O)g
 CC=$(O)c -w
@@ -36,6 +36,7 @@ O1=\
 O2=\
 	os_file.$O\
 	os_time.$O\
+	os_env.$O\
 
 $(PKG): a1 a2
 a1:	$(O1)

src/lib/os/os_env.go

+// Copyright 2009 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.
+
+// Environment variables.
+// Setenv doesn't exist yet: don't have the run-time hooks yet
+
+package os
+
+import os "os"
+
+export var (
+	ENOENV = NewError("no such environment variable");
+)
+
+export func Getenv(s string) (v string, err *Error) {
+	n := len(s);
+	if n == 0 {
+		return "", EINVAL
+	}
+	for i := 0; i < sys.envc(); i++ {
+		e := sys.envv(i);
+		if len(e) > n && e[n] == '=' && e[0 : n] == s {
+			return e[n+1 : len(e)], nil
+		}
+	}
+	return "", ENOENV
+}

test/env.go

+// $G $F.go && $L $F.$A && ./$A.out
+
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+import os "os"
+
+func main() {
+	ga, e0 := os.Getenv("GOARCH");
+	if e0 != nil {
+		print("$GOARCH: ", e0.String(), "\n");
+		sys.exit(1);
+	}
+	if ga != "amd64" {
+		print("$GOARCH=", ga, "\n");
+		sys.exit(1);
+	}
+	xxx, e1 := os.Getenv("DOES_NOT_EXIST");
+	if e1 != os.ENOENV {
+		print("$DOES_NOT_EXIST=", xxx, "; err = ", e1.String(), "\n");
+		sys.exit(1);
+	}
+}