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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 run implements the ``go run'' command.
package run
import (
var CmdRun = &base.Command{
UsageLine: "go run [build flags] [-exec xprog] package [arguments...]",
Short: "compile and run Go program",
Long: `
Run compiles and runs the named main Go package.
Typically the package is specified as a list of .go source files,
but it may also be an import path, file system path, or pattern
matching a single known package, as in 'go run .' or 'go run my/cmd'.
By default, 'go run' runs the compiled binary directly: 'a.out arguments...'.
If the -exec flag is given, 'go run' invokes the binary using xprog:
'xprog a.out arguments...'.
If the -exec flag is not given, GOOS or GOARCH is different from the system
default, and a program named go_$GOOS_$GOARCH_exec can be found
on the current search path, 'go run' invokes the binary using that program,
for example 'go_nacl_386_exec a.out arguments...'. This allows execution of
cross-compiled programs when a simulator or other execution method is
The exit status of Run is not the exit status of the compiled binary.
For more about build flags, see 'go help build'.
For more about specifying packages, see 'go help packages'.
See also: go build.
func init() {
CmdRun.Run = runRun // break init loop
CmdRun.Flag.Var((*base.StringsFlag)(&work.ExecCmd), "exec", "")
func printStderr(args ...interface{}) (int, error) {
return fmt.Fprint(os.Stderr, args...)
func runRun(cmd *base.Command, args []string) {
var b work.Builder
b.Print = printStderr
i := 0
for i < len(args) && strings.HasSuffix(args[i], ".go") {
var p *load.Package
if i > 0 {
files := args[:i]
for _, file := range files {
if strings.HasSuffix(file, "_test.go") {
// GoFilesPackage is going to assign this to TestGoFiles.
// Reject since it won't be part of the build.
base.Fatalf("go run: cannot run *_test.go files (%s)", file)
p = load.GoFilesPackage(files)
} else if len(args) > 0 && !strings.HasPrefix(args[0], "-") {
pkgs := load.PackagesAndErrors(args[:1])
if len(pkgs) > 1 {
var names []string
for _, p := range pkgs {
names = append(names, p.ImportPath)
base.Fatalf("go run: pattern %s matches multiple packages:\n\t%s", args[0], strings.Join(names, "\n\t"))
p = pkgs[0]
} else {
base.Fatalf("go run: no go files listed")
cmdArgs := args[i:]
if p.Error != nil {
base.Fatalf("%s", p.Error)
p.Internal.OmitDebug = true
if len(p.DepsErrors) > 0 {
// Since these are errors in dependencies,
// the same error might show up multiple times,
// once in each package that depends on it.
// Only print each once.
printed := map[*load.PackageError]bool{}
for _, err := range p.DepsErrors {
if !printed[err] {
printed[err] = true
base.Errorf("%s", err)
if p.Name != "main" {
base.Fatalf("go run: cannot run non-main package")
p.Target = "" // must build - not up to date
var src string
if len(p.GoFiles) > 0 {
src = p.GoFiles[0]
} else if len(p.CgoFiles) > 0 {
src = p.CgoFiles[0]
} else {
// this case could only happen if the provided source uses cgo
// while cgo is disabled.
hint := ""
if !cfg.BuildContext.CgoEnabled {
hint = " (cgo is disabled)"
base.Fatalf("go run: no suitable source files%s", hint)
p.Internal.ExeName = src[:len(src)-len(".go")] // name temporary executable for first go file
a1 := b.LinkAction(work.ModeBuild, work.ModeBuild, p)
a := &work.Action{Mode: "go run", Func: buildRunProgram, Args: cmdArgs, Deps: []*work.Action{a1}}
// buildRunProgram is the action for running a binary that has already
// been compiled. We ignore exit status.
func buildRunProgram(b *work.Builder, a *work.Action) error {
cmdline := str.StringList(work.FindExecCmd(), a.Deps[0].Target, a.Args)
if cfg.BuildN || cfg.BuildX {
b.Showcmd("", "%s", strings.Join(cmdline, " "))
if cfg.BuildN {
return nil
return nil