Fix tty/console output prompt when piping to a file.

lib/UserInterface/textinput/TerminalDisplayUnix.cpp

@@ -17,6 +17,7 @@
 
 #include "textinput/TerminalDisplayUnix.h"
 
+#include <fcntl.h>
 #include <stdio.h>
 // putenv not in cstdlib on Solaris
 #include <stdlib.h>
@@ -114,17 +115,33 @@ namespace textinput {
     if (TERM &&  strstr(TERM, "256")) {
       fNColors = 256;
     }
+    fOutputID = STDOUT_FILENO;
+    if (::isatty(::fileno(stdin)) && !::isatty(fOutputID)) {
+      // Display prompt, even if stdout is going somewhere else
+      fOutputID = ::open("/dev/tty", O_WRONLY);
+      SetIsTTY(true);
+    }
+  }
+
+  static void syncOut(int fd) {
+    ::fsync(fd);
+    //if (fd != STDOUT_FILENO)
+      ::fflush(stdout);
   }
 
   TerminalDisplayUnix::~TerminalDisplayUnix() {
     Detach();
+    if (fOutputID != STDOUT_FILENO) {
+      syncOut(fOutputID);
+      ::close(fOutputID);
+    }
   }
 
   void
   TerminalDisplayUnix::HandleResizeSignal() {
 #ifdef TIOCGWINSZ
     struct winsize sz;
-    int ret = ioctl(fileno(stdout), TIOCGWINSZ, (char*)&sz);
+    int ret = ioctl(fOutputID, TIOCGWINSZ, (char*)&sz);
     if (!ret && sz.ws_col) {
       SetWidth(sz.ws_col);
 
@@ -245,7 +262,7 @@ namespace textinput {
   /// \param[in] len length of the raw string
   void
   TerminalDisplayUnix::WriteRawString(const char *text, size_t len) {
-    if (write(fileno(stdout), text, len) == -1) {
+    if (write(fOutputID, text, len) == -1) {
       // Silence Ubuntu's "unused result". We don't care if it fails.
     }
   }
@@ -264,7 +281,7 @@ namespace textinput {
   TerminalDisplayUnix::Attach() {
     // set to noecho
     if (fIsAttached) return;
-    fflush(stdout);
+    syncOut(fOutputID);
     TerminalConfigUnix::Get().Attach();
     fWritePos = Pos();
     fWriteLen = 0;
@@ -274,7 +291,7 @@ namespace textinput {
   void
   TerminalDisplayUnix::Detach() {
     if (!fIsAttached) return;
-    fflush(stdout);
+    syncOut(fOutputID);
     TerminalConfigUnix::Get().Detach();
     TerminalDisplay::Detach();
     fIsAttached = false;

lib/UserInterface/textinput/TerminalDisplayUnix.h

@@ -50,6 +50,7 @@ namespace textinput {
   private:
     bool fIsAttached; // whether tty is configured
     size_t fNColors; // number of colors supported by output
+    int fOutputID; // Prompt output file descriptor
   };
 }
 #endif // TEXTINPUT_TERMINALDISPLAYUNIX_H