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// 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 main
import (
var cmdList = &Command{
UsageLine: "list [-e] [-f format] [-json] [build flags] [packages]",
Short: "list packages",
Long: `
List lists the packages named by the import paths, one per line.
The default output shows the package import path:
The -f flag specifies an alternate format for the list, using the
syntax of package template. The default output is equivalent to -f
'{{.ImportPath}}'. The struct being passed to the template is:
type Package struct {
Dir string // directory containing package sources
ImportPath string // import path of package in dir
Name string // package name
Doc string // package documentation string
Target string // install path
Goroot bool // is this package in the Go root?
Standard bool // is this package part of the standard Go library?
Stale bool // would 'go install' do anything for this package?
Root string // Go root or Go path dir containing this package
// Source files
GoFiles []string // .go source files (excluding CgoFiles, TestGoFiles, XTestGoFiles)
CgoFiles []string // .go sources files that import "C"
IgnoredGoFiles []string // .go sources ignored due to build constraints
CFiles []string // .c source files
CXXFiles []string // .cc, .cxx and .cpp source files
MFiles []string // .m source files
HFiles []string // .h, .hh, .hpp and .hxx source files
SFiles []string // .s source files
SwigFiles []string // .swig files
SwigCXXFiles []string // .swigcxx files
SysoFiles []string // .syso object files to add to archive
// Cgo directives
CgoCFLAGS []string // cgo: flags for C compiler
CgoCPPFLAGS []string // cgo: flags for C preprocessor
CgoCXXFLAGS []string // cgo: flags for C++ compiler
CgoLDFLAGS []string // cgo: flags for linker
CgoPkgConfig []string // cgo: pkg-config names
// Dependency information
Imports []string // import paths used by this package
Deps []string // all (recursively) imported dependencies
// Error information
Incomplete bool // this package or a dependency has an error
Error *PackageError // error loading package
DepsErrors []*PackageError // errors loading dependencies
TestGoFiles []string // _test.go files in package
TestImports []string // imports from TestGoFiles
XTestGoFiles []string // _test.go files outside package
XTestImports []string // imports from XTestGoFiles
The template function "join" calls strings.Join.
The template function "context" returns the build context, defined as:
type Context struct {
GOARCH string // target architecture
GOOS string // target operating system
GOROOT string // Go root
GOPATH string // Go path
CgoEnabled bool // whether cgo can be used
UseAllFiles bool // use files regardless of +build lines, file names
Compiler string // compiler to assume when computing target paths
BuildTags []string // build constraints to match in +build lines
ReleaseTags []string // releases the current release is compatible with
InstallSuffix string // suffix to use in the name of the install dir
For more information about the meaning of these fields see the documentation
for the go/build package's Context type.
The -json flag causes the package data to be printed in JSON format
instead of using the template format.
The -e flag changes the handling of erroneous packages, those that
cannot be found or are malformed. By default, the list command
prints an error to standard error for each erroneous package and
omits the packages from consideration during the usual printing.
With the -e flag, the list command never prints errors to standard
error and instead processes the erroneous packages with the usual
printing. Erroneous packages will have a non-empty ImportPath and
a non-nil Error field; other information may or may not be missing
For more about build flags, see 'go help build'.
For more about specifying packages, see 'go help packages'.
func init() {
cmdList.Run = runList // break init cycle
var listE = cmdList.Flag.Bool("e", false, "")
var listFmt = cmdList.Flag.String("f", "{{.ImportPath}}", "")
var listJson = cmdList.Flag.Bool("json", false, "")
var nl = []byte{'\n'}
func runList(cmd *Command, args []string) {
out := newTrackingWriter(os.Stdout)
defer out.w.Flush()
var do func(*Package)
if *listJson {
do = func(p *Package) {
b, err := json.MarshalIndent(p, "", "\t")
if err != nil {
fatalf("%s", err)
} else {
var cachedCtxt *Context
context := func() *Context {
if cachedCtxt == nil {
cachedCtxt = newContext(&buildContext)
return cachedCtxt
fm := template.FuncMap{
"join": strings.Join,
"context": context,
tmpl, err := template.New("main").Funcs(fm).Parse(*listFmt)
if err != nil {
fatalf("%s", err)
do = func(p *Package) {
if err := tmpl.Execute(out, p); err != nil {
fatalf("%s", err)
if out.NeedNL() {
load := packages
if *listE {
load = packagesAndErrors
for _, pkg := range load(args) {
// TrackingWriter tracks the last byte written on every write so
// we can avoid printing a newline if one was already written or
// if there is no output at all.
type TrackingWriter struct {
w *bufio.Writer
last byte
func newTrackingWriter(w io.Writer) *TrackingWriter {
return &TrackingWriter{
w: bufio.NewWriter(w),
last: '\n',
func (t *TrackingWriter) Write(p []byte) (n int, err error) {
n, err = t.w.Write(p)
if n > 0 {
t.last = p[n-1]
func (t *TrackingWriter) Flush() {
func (t *TrackingWriter) NeedNL() bool {
return t.last != '\n'