[dev.cc] cmd/dist: show bootstrap build progress in real time

Change-Id: I97bbf7a276c8f99554f0e3a9bcc8d3792a5e0f65
Reviewed-on: https://go-review.googlesource.com/3221
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

diff --git a/src/cmd/dist/util.go b/src/cmd/dist/util.go
index 1bb3ba80e6795603d8c8a5a618d152080a3136f5..decbb0ffd2f8d807b93488ffea3a810d30f4684b 100644 (file)
--- a/src/cmd/dist/util.go
+++ b/src/cmd/dist/util.go
@@ -84,8 +84,23 @@ func run(dir string, mode int, cmd ...string) string {
 
        xcmd := exec.Command(cmd[0], cmd[1:]...)
        xcmd.Dir = dir
+       var data []byte
        var err error
-       data, err := xcmd.CombinedOutput()
+
+       // If we want to show command output and this is not
+       // a background command, assume it's the only thing
+       // running, so we can just let it write directly stdout/stderr
+       // as it runs without fear of mixing the output with some
+       // other command's output. Not buffering lets the output
+       // appear as it is printed instead of once the command exits.
+       // This is most important for the invocation of 'go1.4 build -v bootstrap/...'.
+       if mode&(Background|ShowOutput) == ShowOutput {
+               xcmd.Stdout = os.Stdout
+               xcmd.Stderr = os.Stderr
+               err = xcmd.Run()
+       } else {
+               data, err = xcmd.CombinedOutput()
+       }
        if err != nil && mode&CheckExit != 0 {
                outputLock.Lock()
                if len(data) > 0 {