os/user: new package to look up users

Only for Unix presently. Other operating systems
are stubbed out, as well as arm (lacks cgo).

R=rsc, r, bradfitzwork
CC=golang-dev
https://golang.org/cl/4440057

src/pkg/Makefile

@@ -120,6 +120,7 @@ DIRS=\
 	netchan\
 	os\
 	os/signal\
+	os/user\
 	patch\
 	path\
 	path/filepath\

src/pkg/os/user/Makefile

+# 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.
+
+include ../../../Make.inc
+
+TARG=os/user
+GOFILES=\
+	user.go\
+
+ifneq ($(GOARCH),arm)
+CGOFILES_linux=\
+	lookup_unix.go
+CGOFILES_freebsd=\
+	lookup_unix.go
+CGOFILES_darwin=\
+	lookup_unix.go
+endif
+
+ifneq ($(CGOFILES_$(GOOS)),)
+CGOFILES+=$(CGOFILES_$(GOOS))
+else
+GOFILES+=lookup_stubs.go
+endif
+
+include ../../../Make.pkg

src/pkg/os/user/lookup_stubs.go

+// 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 user
+
+import (
+	"fmt"
+	"os"
+	"runtime"
+)
+
+func Lookup(username string) (*User, os.Error) {
+	return nil, fmt.Errorf("user: Lookup not implemented on %s/%s", runtime.GOOS, runtime.GOARCH)
+}
+
+func LookupId(int) (*User, os.Error) {
+	return nil, fmt.Errorf("user: LookupId not implemented on %s/%s", runtime.GOOS, runtime.GOARCH)
+}

src/pkg/os/user/lookup_unix.go

+// 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 user
+
+import (
+	"fmt"
+	"os"
+	"runtime"
+	"strings"
+	"unsafe"
+)
+
+/*
+#include <unistd.h>
+#include <sys/types.h>
+#include <pwd.h>
+#include <stdlib.h>
+
+static int mygetpwuid_r(int uid, struct passwd *pwd,
+	char *buf, size_t buflen, struct passwd **result) {
+ return getpwuid_r(uid, pwd, buf, buflen, result);
+}
+*/
+import "C"
+
+// Lookup looks up a user by username. If the user cannot be found,
+// the returned error is of type UnknownUserError.
+func Lookup(username string) (*User, os.Error) {
+	return lookup(-1, username, true)
+}
+
+// LookupId looks up a user by userid. If the user cannot be found,
+// the returned error is of type UnknownUserIdError.
+func LookupId(uid int) (*User, os.Error) {
+	return lookup(uid, "", false)
+}
+
+func lookup(uid int, username string, lookupByName bool) (*User, os.Error) {
+	var pwd C.struct_passwd
+	var result *C.struct_passwd
+
+	var bufSize C.long
+	if runtime.GOOS == "freebsd" {
+		// FreeBSD doesn't have _SC_GETPW_R_SIZE_MAX
+		// and just returns -1.  So just use the same
+		// size that Linux returns
+		bufSize = 1024
+	} else {
+		bufSize = C.sysconf(C._SC_GETPW_R_SIZE_MAX)
+		if bufSize <= 0 || bufSize > 1<<20 {
+			return nil, fmt.Errorf("user: unreasonable _SC_GETPW_R_SIZE_MAX of %d", bufSize)
+		}
+	}
+	buf := C.malloc(C.size_t(bufSize))
+	defer C.free(buf)
+	var rv C.int
+	if lookupByName {
+		nameC := C.CString(username)
+		defer C.free(unsafe.Pointer(nameC))
+		rv = C.getpwnam_r(nameC,
+			&pwd,
+			(*C.char)(buf),
+			C.size_t(bufSize),
+			&result)
+		if rv != 0 {
+			return nil, fmt.Errorf("user: lookup username %s: %s", username, os.Errno(rv))
+		}
+		if result == nil {
+			return nil, UnknownUserError(username)
+		}
+	} else {
+		// mygetpwuid_r is a wrapper around getpwuid_r to
+		// to avoid using uid_t because C.uid_t(uid) for
+		// unknown reasons doesn't work on linux.
+		rv = C.mygetpwuid_r(C.int(uid),
+			&pwd,
+			(*C.char)(buf),
+			C.size_t(bufSize),
+			&result)
+		if rv != 0 {
+			return nil, fmt.Errorf("user: lookup userid %d: %s", uid, os.Errno(rv))
+		}
+		if result == nil {
+			return nil, UnknownUserIdError(uid)
+		}
+	}
+	u := &User{
+		Uid:      int(pwd.pw_uid),
+		Gid:      int(pwd.pw_gid),
+		Username: C.GoString(pwd.pw_name),
+		Name:     C.GoString(pwd.pw_gecos),
+		HomeDir:  C.GoString(pwd.pw_dir),
+	}
+	// The pw_gecos field isn't quite standardized.  Some docs
+	// say: "It is expected to be a comma separated list of
+	// personal data where the first item is the full name of the
+	// user."
+	if i := strings.Index(u.Name, ","); i >= 0 {
+		u.Name = u.Name[:i]
+	}
+	return u, nil
+}

src/pkg/os/user/user.go

+// 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 user allows user account lookups by name or id.
+package user
+
+import (
+	"strconv"
+)
+
+// User represents a user account.
+type User struct {
+	Uid      int // user id
+	Gid      int // primary group id
+	Username string
+	Name     string
+	HomeDir  string
+}
+
+// UnknownUserIdError is returned by LookupId when
+// a user cannot be found.
+type UnknownUserIdError int
+
+func (e UnknownUserIdError) String() string {
+	return "user: unknown userid " + strconv.Itoa(int(e))
+}
+
+// UnknownUserError is returned by Lookup when
+// a user cannot be found.
+type UnknownUserError string
+
+func (e UnknownUserError) String() string {
+	return "user: unknown user " + string(e)
+}

src/pkg/os/user/user_test.go

+// 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 user
+
+import (
+	"os"
+	"reflect"
+	"runtime"
+	"syscall"
+	"testing"
+)
+
+func skip(t *testing.T) bool {
+	if runtime.GOARCH == "arm" {
+		t.Logf("user: cgo not implemented on arm; skipping tests")
+		return true
+	}
+
+	if runtime.GOOS == "linux" || runtime.GOOS == "freebsd" || runtime.GOOS == "darwin" {
+		return false
+	}
+
+	t.Logf("user: Lookup not implemented on %s; skipping test", runtime.GOOS)
+	return true
+}
+
+func TestLookup(t *testing.T) {
+	if skip(t) {
+		return
+	}
+
+	// Test LookupId on the current user
+	uid := syscall.Getuid()
+	u, err := LookupId(uid)
+	if err != nil {
+		t.Fatalf("LookupId: %v", err)
+	}
+	if e, g := uid, u.Uid; e != g {
+		t.Errorf("expected Uid of %d; got %d", e, g)
+	}
+	fi, err := os.Stat(u.HomeDir)
+	if err != nil || !fi.IsDirectory() {
+		t.Errorf("expected a valid HomeDir; stat(%q): err=%v, IsDirectory=%v", err, fi.IsDirectory())
+	}
+	if u.Username == "" {
+		t.Fatalf("didn't get a username")
+	}
+
+	// Test Lookup by username, using the username from LookupId
+	un, err := Lookup(u.Username)
+	if err != nil {
+		t.Fatalf("Lookup: %v", err)
+	}
+	if !reflect.DeepEqual(u, un) {
+		t.Errorf("Lookup by userid vs. name didn't match\n"+
+			"LookupId(%d): %#v\n"+
+			"Lookup(%q): %#v\n",uid, u, u.Username, un)
+	}
+}