Complete the query-response system.

Some commands now can be queried from a remote session using the
'-Q' flag, e.g. 'screen -Q windows'. The commands will send the
response to the stdout of the querying process. If there was an
error in the command, then the querying process will exit with
a non-zero status.

The commands that can be queried now are:
  echo
  info
  lastmsg
  time
  title
  windows

5 files changed, 57 insertions, 26 deletions

diff --git a/src/attacher.c b/src/attacher.c
index f8c3217..ef3ce8b 100644
--- a/src/attacher.c
+++ b/src/attacher.c
@@ -1009,6 +1009,16 @@ int query;
 	  if ((r = MakeServerSocket()) >= 0)
 	    break;
 	}
+      if (r < 0)
+	{
+	  for (c = '0'; c <= '9'; c++)
+	    {
+	      query[6] = c;
+	      strcpy(sp, query);
+	      if ((r = MakeServerSocket()) >= 0)
+		break;
+	    }
+	}
 
       if (r < 0)
 	Panic(0, "Could not create a listening socket to read the results.");
@@ -1040,3 +1050,4 @@ int query;
       close(s);
     }
 }
+
diff --git a/src/comm.c b/src/comm.c
index f7730cc..4843e10 100644
--- a/src/comm.c
+++ b/src/comm.c
@@ -180,7 +180,7 @@ struct comm comms[RC_LAST + 1] =
   { "dinfo",		NEED_DISPLAY|ARGS_0 },
   { "displays",		NEED_LAYER|ARGS_0 },
   { "dumptermcap",	NEED_FORE|ARGS_0 },
-  { "echo",		ARGS_12 },
+  { "echo",		CAN_QUERY|ARGS_12 },
 #ifdef ENCODINGS
   { "encoding",		ARGS_12 },
 #endif
@@ -311,8 +311,8 @@ struct comm comms[RC_LAST + 1] =
   { "termcap",		ARGS_23 },
   { "termcapinfo",	ARGS_23 },
   { "terminfo",		ARGS_23 },
-  { "time",		ARGS_01 },
-  { "title",		NEED_FORE|ARGS_01 },
+  { "time",		CAN_QUERY|ARGS_01 },
+  { "title",		CAN_QUERY|NEED_FORE|ARGS_01 },
   { "umask",		ARGS_1|ARGS_ORMORE },
   { "unbindall",	ARGS_0 },
   { "unsetenv",		ARGS_1 },
@@ -327,7 +327,7 @@ struct comm comms[RC_LAST + 1] =
   { "wall",		NEED_DISPLAY|ARGS_1},
   { "width",		ARGS_0123 },
   { "windowlist",	ARGS_012 },
-  { "windows",		NEED_DISPLAY|ARGS_0 },
+  { "windows",		CAN_QUERY|ARGS_0 },
   { "wrap",		NEED_FORE|ARGS_01 },
 #ifdef COPY_PASTE
   { "writebuf",		ARGS_0123 },
diff --git a/src/process.c b/src/process.c
index 923565a..5d6941d 100644
--- a/src/process.c
+++ b/src/process.c
@@ -59,6 +59,7 @@ extern char *BellString, *ActivityString, *ShellProg, *ShellArgs[];
 extern char *hstatusstring, *captionstring, *timestring;
 extern char *wliststr, *wlisttit;
 extern int captionalways;
+extern int queryflag;
 extern char *hardcopydir, *screenlogfile, *logtstamp_string;
 extern int log_flush, logtstamp_on, logtstamp_after;
 extern char *VisualBellString;
@@ -1147,31 +1148,35 @@ int key;
       return;
     }
   n = comms[nr].flags;
-  /* XXX: Commands will have a CAN_QUERY flag, depending on whether they have
-     something to return on a query. For example, 'windows' can return a result,
-     but 'other' cannot.
+  /* Commands will have a CAN_QUERY flag, depending on whether they have
+   * something to return on a query. For example, 'windows' can return a result,
+   * but 'other' cannot.
+   * If some command causes an error, then it should reset queryflag to -1, so that
+   * the process requesting the query can be notified that an error happened.
    */
-#if 0
-  if (!(n & CAN_QUERY) && queryflag)
+  if (!(n & CAN_QUERY) && queryflag >= 0)
     {
       /* Query flag is set, but this command cannot be queried. */
       Msg(0, "%s command cannot be queried.", comms[nr].name);
+      queryflag = -1;
       return;
     }
-#endif
   if ((n & NEED_DISPLAY) && display == 0)
     {
       Msg(0, "%s: %s: display required", rc_name, comms[nr].name);
+      queryflag = -1;
       return;
     }
   if ((n & NEED_FORE) && fore == 0)
     {
       Msg(0, "%s: %s: window required", rc_name, comms[nr].name);
+      queryflag = -1;
       return;
     }
   if ((n & NEED_LAYER) && flayer == 0)
     {
       Msg(0, "%s: %s: display or window required", rc_name, comms[nr].name);
+      queryflag = -1;
       return;
     }
   if ((argc = CheckArgNum(nr, args)) < 0)
@@ -1183,6 +1188,7 @@ int key;
         {
 	  Msg(0, "%s: %s: permission denied (user %s)", 
 	      rc_name, comms[nr].name, (EffectiveAclUser ? EffectiveAclUser : D_user)->u_name);
+	  queryflag = -1;
 	  return;
 	}
     }
@@ -2038,6 +2044,13 @@ int key;
       }
       break;
     case RC_TITLE:
+      if (queryflag >= 0)
+	{
+	  if (fore)
+	    Msg(0, "%s", fore->w_title);
+	  else
+	    queryflag = -1;
+	}
       if (*args == 0)
 	InputAKA();
       else
@@ -2647,7 +2660,10 @@ int key;
       if (s)
 	Msg(0, "%s", s);
       else
-	Msg(0, "%s: 'echo [-n] [-p] \"string\"' expected.", rc_name);
+	{
+	  Msg(0, "%s: 'echo [-n] [-p] \"string\"' expected.", rc_name);
+	  queryflag = -1;
+	}
       break;
     case RC_BELL:
     case RC_BELL_MSG:
@@ -5330,7 +5346,7 @@ int where;
 	continue;
       if ((flags & 1) && display && p == D_fore)
 	continue;
-      if (D_fore && D_fore->w_group != p->w_group)
+      if (display && D_fore && D_fore->w_group != p->w_group)
 	continue;
 
       cmd = p->w_title;
@@ -5472,13 +5488,11 @@ int where;
   char buf[1024];
   char *s, *ss;
 
-  if (!display)
-    return;
-  if (where == -1 && D_fore)
+  if (display && where == -1 && D_fore)
     where = D_fore->w_number;
   ss = AddWindows(buf, sizeof(buf), 0, where);
   s = buf + strlen(buf);
-  if (ss - buf > D_width / 2)
+  if (display && ss - buf > D_width / 2)
     {
       ss -= D_width / 2;
       if (s - ss < D_width)
diff --git a/src/screen.c b/src/screen.c
index ce081ac..67cddbc 100644
--- a/src/screen.c
+++ b/src/screen.c
@@ -207,7 +207,7 @@ char *wlisttit;
 int auto_detach = 1;
 int iflag, rflag, dflag, lsflag, quietflag, wipeflag, xflag;
 int cmdflag;
-int queryflag;
+int queryflag = -1;
 int adaptflag;
 
 #ifdef MULTIUSER
@@ -1181,7 +1181,7 @@ char **av;
       if (!*av)
 	Panic(0, "Please specify a command.");
       SET_GUID();
-      SendCmdMessage(sty, SockMatch, av, queryflag);
+      SendCmdMessage(sty, SockMatch, av, queryflag >= 0);
       exit(0);
     }
   else if (rflag || xflag)
@@ -2110,6 +2110,9 @@ VA_DECL
     }
   else
     printf("%s\r\n", buf);
+
+  if (queryflag >= 0)
+    write(queryflag, buf, strlen(buf));
 }
 
 /*
diff --git a/src/socket.c b/src/socket.c
index 08b545f..70b57db 100644
--- a/src/socket.c
+++ b/src/socket.c
@@ -65,6 +65,7 @@ static void  AskPassword __P((struct msg *));
 extern char *RcFileName, *extra_incap, *extra_outcap;
 extern int ServerSocket, real_uid, real_gid, eff_uid, eff_gid;
 extern int dflag, iflag, rflag, lsflag, quietflag, wipeflag, xflag;
+extern int queryflag;
 extern char *attach_tty, *LoginName, HostName[];
 extern struct display *display, *displays;
 extern struct win *fore, **wtab, *console_window, *windows;
@@ -1171,12 +1172,6 @@ ReceiveMsg()
       break;
 #endif
     case MSG_QUERY:
-      /* Reset error buffer */
-      /* Reset output buffer */
-      /* FALLTHROUGH */
-    case MSG_COMMAND:
-      DoCommandMsg(&m);
-      if (m.type == MSG_QUERY)
 	{
 	  char *oldSockPath = SaveStr(SockPath);
 	  strcpy(SockPath, m.m.command.writeback);
@@ -1185,12 +1180,20 @@ ReceiveMsg()
 	  Free(oldSockPath);
 	  if (s >= 0)
 	    {
-	      write(s, "So ...", 7);
+	      queryflag = s;
+	      DoCommandMsg(&m);
 	      close(s);
 	    }
-	  Kill(m.m.command.apid, SIGCONT);	/* Send SIG_BYE if an error happened, instead */
+	  else
+	    queryflag = -1;
+
+	  Kill(m.m.command.apid, (queryflag >= 0) ? SIGCONT : SIG_BYE);	/* Send SIG_BYE if an error happened */
+	  queryflag = -1;
 	}
       break;
+    case MSG_COMMAND:
+      DoCommandMsg(&m);
+      break;
     default:
       Msg(0, "Invalid message (type %d).", m.type);
     }