os: add Expand function to evaluate environment variables.
Fixes #1258.
R=gri, msolo, bradfitzpatrick, r2
CC=golang-dev
https://golang.org/cl/2988041
diff --git a/src/pkg/os/env_test.go b/src/pkg/os/env_test.go
new file mode 100644
index 0000000..04ff390
--- /dev/null
+++ b/src/pkg/os/env_test.go
@@ -0,0 +1,59 @@
+// 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 os_test
+
+import (
+ . "os"
+ "testing"
+)
+
+// testGetenv gives us a controlled set of variables for testing Expand.
+func testGetenv(s string) string {
+ switch s {
+ case "*":
+ return "all the args"
+ case "#":
+ return "NARGS"
+ case "$":
+ return "PID"
+ case "1":
+ return "ARGUMENT1"
+ case "HOME":
+ return "/usr/gopher"
+ case "H":
+ return "(Value of H)"
+ case "home_1":
+ return "/usr/foo"
+ case "_":
+ return "underscore"
+ }
+ return ""
+}
+
+var expandTests = []struct {
+ in, out string
+}{
+ {"", ""},
+ {"$*", "all the args"},
+ {"$$", "PID"},
+ {"${*}", "all the args"},
+ {"$1", "ARGUMENT1"},
+ {"${1}", "ARGUMENT1"},
+ {"now is the time", "now is the time"},
+ {"$HOME", "/usr/gopher"},
+ {"$home_1", "/usr/foo"},
+ {"${HOME}", "/usr/gopher"},
+ {"${H}OME", "(Value of H)OME"},
+ {"A$$$#$1$H$home_1*B", "APIDNARGSARGUMENT1(Value of H)/usr/foo*B"},
+}
+
+func TestExpand(t *testing.T) {
+ for _, test := range expandTests {
+ result := Expand(test.in, testGetenv)
+ if result != test.out {
+ t.Errorf("Expand(%q)=%q; expected %q", test.in, result, test.out)
+ }
+ }
+}
