os: add ExitCode method to ProcessState

Fixes #26539

Change-Id: I6d403c1bbb552e1f1bdcc09a7ccd60b50617e0fc
GitHub-Last-Rev: 0b5262df5d
GitHub-Pull-Request: golang/go#26544
Reviewed-on: https://go-review.googlesource.com/125443
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

src/os/exec/exec_test.go

@@ -168,6 +168,49 @@ func TestExitStatus(t *testing.T) {
 	}
 }
 
+func TestExitCode(t *testing.T) {
+	// Test that exit code are returned correctly
+	cmd := helperCommand(t, "exit", "42")
+	cmd.Run()
+	want := 42
+	got := cmd.ProcessState.ExitCode()
+	if want != got {
+		t.Errorf("ExitCode got %d, want %d", got, want)
+	}
+
+	cmd = helperCommand(t, "/no-exist-executable")
+	cmd.Run()
+	want = 2
+	got = cmd.ProcessState.ExitCode()
+	if want != got {
+		t.Errorf("ExitCode got %d, want %d", got, want)
+	}
+
+	cmd = helperCommand(t, "exit", "255")
+	cmd.Run()
+	want = 255
+	got = cmd.ProcessState.ExitCode()
+	if want != got {
+		t.Errorf("ExitCode got %d, want %d", got, want)
+	}
+
+	cmd = helperCommand(t, "cat")
+	cmd.Run()
+	want = 0
+	got = cmd.ProcessState.ExitCode()
+	if want != got {
+		t.Errorf("ExitCode got %d, want %d", got, want)
+	}
+
+	// Test when command does not call Run().
+	cmd = helperCommand(t, "cat")
+	want = -1
+	got = cmd.ProcessState.ExitCode()
+	if want != got {
+		t.Errorf("ExitCode got %d, want %d", got, want)
+	}
+}
+
 func TestPipes(t *testing.T) {
 	check := func(what string, err error) {
 		if err != nil {

src/os/exec_plan9.go

@@ -136,3 +136,13 @@ func (p *ProcessState) String() string {
 	}
 	return "exit status: " + p.status.Msg
 }
+
+// ExitCode returns the exit code of the exited process, or -1
+// if the process hasn't exited or was terminated by a signal.
+func (p *ProcessState) ExitCode() int {
+	// return -1 if the process hasn't started.
+	if p == nil {
+		return -1
+	}
+	return p.status.ExitStatus()
+}

src/os/exec_posix.go

@@ -106,3 +106,13 @@ func (p *ProcessState) String() string {
 	}
 	return res
 }
+
+// ExitCode returns the exit code of the exited process, or -1
+// if the process hasn't exited or was terminated by a signal.
+func (p *ProcessState) ExitCode() int {
+	// return -1 if the process hasn't started.
+	if p == nil {
+		return -1
+	}
+	return p.status.ExitStatus()
+}