Add a library for running external commands, providing timeouts and test injection.

ct/go/util/util.go

Index: ct/go/util/util.go
diff --git a/ct/go/util/util.go b/ct/go/util/util.go
index 1a22fe57b2d2f767d0805136488ecb911c4f74c2..6b9afb013281967fb67bba823466be8718185ffd 100644
--- a/ct/go/util/util.go
+++ b/ct/go/util/util.go
@@ -6,12 +6,11 @@ import (
 	"fmt"
 	"io/ioutil"
 	"os"
-	"os/exec"
 	"path/filepath"
 	"strconv"
-	"strings"
 	"time"
 
+	"go.skia.org/infra/go/exec"
 	"go.skia.org/infra/go/util"
 
 	"github.com/skia-dev/glog"
@@ -86,63 +85,23 @@ func TimeTrack(start time.Time, name string) {
 	glog.Infof("===== %s took %s =====", name, elapsed)
 }
 
-// WriteLog implements the io.Writer interface and writes to glog and an output
-// file (if specified).
-type WriteLog struct {
-	LogFunc    func(format string, args ...interface{})
-	OutputFile *os.File
-}
-
-func (wl WriteLog) Write(p []byte) (n int, err error) {
-	wl.LogFunc("%s", string(p))
-	// Write to file if specified.
-	if wl.OutputFile != nil {
-		if n, err := wl.OutputFile.WriteString(string(p)); err != nil {
-			glog.Errorf("Could not write to %s: %s", wl.OutputFile.Name(), err)
-			return n, err
-		}
-	}
-	return len(p), nil
-}
-
 // ExecuteCmd executes the specified binary with the specified args and env.
 // Stdout and Stderr are written to stdoutFile and stderrFile respectively if
 // specified. If not specified then stdout and stderr will be outputted only to
 // glog. Note: It is the responsibility of the caller to close stdoutFile and
 // stderrFile.
 func ExecuteCmd(binary string, args, env []string, timeout time.Duration, stdoutFile, stderrFile *os.File) error {
-	// Add the current PATH to the env.
-	env = append(env, "PATH="+os.Getenv("PATH"))
-
-	// Create the cmd obj.
-	cmd := exec.Command(binary, args...)
-	cmd.Env = env
-
-	// Attach WriteLog to command.
-	cmd.Stdout = WriteLog{LogFunc: glog.Infof, OutputFile: stdoutFile}
-	cmd.Stderr = WriteLog{LogFunc: glog.Errorf, OutputFile: stderrFile}
-
-	// Execute cmd.
-	glog.Infof("Executing %s %s", strings.Join(cmd.Env, " "), strings.Join(cmd.Args, " "))
-	util.LogErr(cmd.Start())
-	done := make(chan error)
-	go func() {
-		done <- cmd.Wait()
-	}()
-	select {
-	case <-time.After(timeout):
-		if err := cmd.Process.Kill(); err != nil {
-			return fmt.Errorf("Failed to kill timed out process: %s", err)
-		}
-		<-done // allow goroutine to exit
-		glog.Errorf("Command killed since it took longer than %f secs", timeout.Seconds())
-		return fmt.Errorf("Command killed since it took longer than %f secs", timeout.Seconds())
-	case err := <-done:
-		if err != nil {
-			return fmt.Errorf("Process done with error: %s", err)
-		}
-	}
-	return nil
+	return exec.Run(&exec.Command{
+		Name:        binary,
+		Args:        args,
+		Env:         env,
+		InheritPath: true,
+		Timeout:     timeout,
+		LogStdout:   true,
+		Stdout:      stdoutFile,
+		LogStderr:   true,
+		Stderr:      stderrFile,
+	})
 }
 
 // SyncDir runs "git pull" and "gclient sync" on the specified directory.