'screen -Q <command>' to get back results.

This is the just the start of querying an existing session. The goal
is to allow something like "windows=`screen -Q windows`" in a bash
script to get back the results from the 'windows' command.

Most of the framework is done. Now the commands need to be updated
to specially deal with the queries.

8 files changed, 138 insertions, 10 deletions

diff --git a/src/attacher.c b/src/attacher.c
index a416ec1..46c14ec 100644
--- a/src/attacher.c
+++ b/src/attacher.c
@@ -83,6 +83,21 @@ AttachSigCont SIGDEFARG
   SIGRETURN;
 }
 
+static int QueryResult;
+
+static sigret_t
+QueryResultSuccess SIGDEFARG
+{
+  QueryResult = 1;
+  SIGRETURN;
+}
+
+static sigret_t
+QueryResultFail SIGDEFARG
+{
+  QueryResult = 2;
+  SIGRETURN;
+}
 
 /*
  *  Send message to a screen backend.
@@ -923,10 +938,11 @@ screen_builtin_lck()
 
 
 void
-SendCmdMessage(sty, match, av)
+SendCmdMessage(sty, match, av, query)
 char *sty;
 char *match;
 char **av;
+int query;
 {
   int i, s;
   struct msg m;
@@ -954,7 +970,7 @@ char **av;
 	exit(1);
     }
   bzero((char *)&m, sizeof(m));
-  m.type = MSG_COMMAND;
+  m.type = query ? MSG_QUERY : MSG_COMMAND;
   if (attach_tty)
     {
       strncpy(m.m_tty, attach_tty, sizeof(m.m_tty) - 1);
@@ -979,7 +995,48 @@ char **av;
   m.m.command.preselect[sizeof(m.m.command.preselect) - 1] = 0;
   m.m.command.apid = getpid();
   debug1("SendCommandMsg writing '%s'\n", m.m.command.cmd);
-  if (WriteMessage(s, &m))
-    Msg(errno, "write");
-  close(s);
+  if (query)
+    {
+      /* Create a server socket so we can get back the result */
+      char *sp = SockPath + strlen(SockPath);
+      char query[] = "-queryX";
+      char c;
+      int r = -1;
+      for (c = 'A'; c <= 'Z'; c++)
+	{
+	  query[6] = c;
+	  strcpy(sp, query);	/* XXX: strncpy? */
+	  if ((r = MakeServerSocket()) >= 0)
+	    break;
+	}
+
+      if (r < 0)
+	Panic(0, "Could not create a listening socket to read the results.");
+
+      strncpy(m.m.command.writeback, SockPath, sizeof(m.m.command.writeback) - 1);
+      m.m.command.writeback[sizeof(m.m.command.writeback) - 1] = '\0';
+
+      /* Send the message, then wait for a response */
+      signal(SIGCONT, QueryResultSuccess);
+      signal(SIG_BYE, QueryResultFail);
+      if (WriteMessage(s, &m))
+	Msg(errno, "write");
+      close(s);
+      while (!QueryResult)
+	pause();
+      signal(SIGCONT, SIG_DFL);
+      signal(SIG_BYE, SIG_DFL);
+
+      /* Read the result and spit it out to stdout */
+      ReceiveRaw(r);
+      unlink(SockPath);
+      if (QueryResult == 2)	/* An error happened */
+	exit(1);
+    }
+  else
+    {
+      if (WriteMessage(s, &m))
+	Msg(errno, "write");
+      close(s);
+    }
 }
diff --git a/src/comm.c b/src/comm.c
index aedfe49..934ad23 100644
--- a/src/comm.c
+++ b/src/comm.c
@@ -206,12 +206,12 @@ struct comm comms[RC_LAST + 1] =
   { "hstatus",		NEED_FORE|ARGS_1 },
   { "idle",		ARGS_0|ARGS_ORMORE },
   { "ignorecase",	ARGS_01 },
-  { "info",		NEED_LAYER|ARGS_0 },
+  { "info",		CAN_QUERY|NEED_LAYER|ARGS_0 },
 #ifdef ENCODINGS
   { "kanji",		NEED_FORE|ARGS_12 },
 #endif
   { "kill",		NEED_FORE|ARGS_0 },
-  { "lastmsg",		NEED_DISPLAY|ARGS_0 },
+  { "lastmsg",		CAN_QUERY|NEED_DISPLAY|ARGS_0 },
   { "layout",           ARGS_1|ARGS_ORMORE},
   { "license",		NEED_LAYER|ARGS_0 },
 #ifdef LOCK
diff --git a/src/comm.sh b/src/comm.sh
index 44c83dd..190de58 100644
--- a/src/comm.sh
+++ b/src/comm.sh
@@ -43,6 +43,8 @@ struct comm
 #define NEED_FORE	(1<<6)	/* this command needs a fore window */
 #define NEED_DISPLAY	(1<<7)	/* this command needs a display */
 #define NEED_LAYER	(1<<8)	/* this command needs a layer */
+#define CAN_QUERY	(1<<9)  /* this command can be queried, i.e. used with -Q to
+				   get back a result to stdout */
 
 #define ARGS_01		(ARGS_0 | ARGS_PLUS1)
 #define ARGS_02		(ARGS_0 | ARGS_PLUS2)
diff --git a/src/extern.h b/src/extern.h
index e3e0a59..9e26883 100644
--- a/src/extern.h
+++ b/src/extern.h
@@ -239,7 +239,7 @@ extern void  FreeTransTable __P((void));
 extern int   Attach __P((int));
 extern void  Attacher __P((void));
 extern sigret_t AttacherFinit __P(SIGPROTOARG);
-extern void  SendCmdMessage __P((char *, char *, char **));
+extern void  SendCmdMessage __P((char *, char *, char **, int));
 
 /* display.c */
 extern struct display *MakeDisplay __P((char *, char *, char *, int, int, struct mode *));
diff --git a/src/process.c b/src/process.c
index fa3d06c..1737dcf 100644
--- a/src/process.c
+++ b/src/process.c
@@ -1144,6 +1144,18 @@ 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.
+   */
+#if 0
+  if (!(n & CAN_QUERY) && queryflag)
+    {
+      /* Query flag is set, but this command cannot be queried. */
+      Msg(0, "%s command cannot be queried.", comms[nr].name);
+      return;
+    }
+#endif
   if ((n & NEED_DISPLAY) && display == 0)
     {
       Msg(0, "%s: %s: display required", rc_name, comms[nr].name);
diff --git a/src/screen.c b/src/screen.c
index e8f4cac..d09359a 100644
--- a/src/screen.c
+++ b/src/screen.c
@@ -205,6 +205,7 @@ char *wlisttit;
 int auto_detach = 1;
 int iflag, rflag, dflag, lsflag, quietflag, wipeflag, xflag;
 int cmdflag;
+int queryflag;
 int adaptflag;
 
 #ifdef MULTIUSER
@@ -678,6 +679,10 @@ char **av;
 		case 'q':
 		  quietflag = 1;
 		  break;
+		case 'Q':
+		  queryflag = 1;
+		  cmdflag = 1;
+		  break;
 		case 'r':
 		case 'R':
 #ifdef MULTI
@@ -1174,7 +1179,7 @@ char **av;
       if (!*av)
 	Panic(0, "Please specify a command.");
       SET_GUID();
-      SendCmdMessage(sty, SockMatch, av);
+      SendCmdMessage(sty, SockMatch, av, queryflag);
       exit(0);
     }
   else if (rflag || xflag)
diff --git a/src/screen.h b/src/screen.h
index d80f0d5..a5145e7 100644
--- a/src/screen.h
+++ b/src/screen.h
@@ -172,6 +172,7 @@ struct mode
 #define MSG_WINCH	6
 #define MSG_HANGUP	7
 #define MSG_COMMAND	8
+#define MSG_QUERY       9
 
 /*
  * versions of struct msg:
@@ -226,6 +227,8 @@ struct msg
 	  char cmd[MAXPATHLEN];	/* command */
 	  int apid;		/* pid of frontend */
 	  char preselect[20];
+	  char writeback[MAXPATHLEN];  /* The socket to write the result.
+					  Only used for MSG_QUERY */
 	}
       command;
       char message[MAXPATHLEN * 2];
diff --git a/src/socket.c b/src/socket.c
index 7832832..965a7d0 100644
--- a/src/socket.c
+++ b/src/socket.c
@@ -1156,14 +1156,58 @@ ReceiveMsg()
 	FinishDetach(&m);
       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);
+	  int s = MakeClientSocket(0);
+	  strcpy(SockPath, oldSockPath);
+	  Free(oldSockPath);
+	  if (s >= 0)
+	    {
+	      write(s, "So ...", 7);
+	      close(s);
+	    }
+	  Kill(m.m.command.apid, SIGCONT);	/* Send SIG_BYE if an error happened, instead */
+	}
       break;
     default:
       Msg(0, "Invalid message (type %d).", m.type);
     }
 }
 
+void
+ReceiveRaw(s)
+int s;
+{
+  char rd[256];
+  int len = 0;
+#ifdef NAMEDPIPE
+  if (fcntl(s, F_SETFL, 0) == -1)
+    Panic(errno, "BLOCK fcntl");
+#else
+  struct sockaddr_un a;
+  len = sizeof(a);
+  if ((s = accept(s, (struct sockaddr *) &a, (void *)&len)) < 0)
+    {
+      Msg(errno, "accept");
+      return;
+    }
+#endif
+  while ((len = read(s, rd, 255)) > 0)
+    {
+      rd[len] = 0;
+      printf("%s", rd);
+    }
+  close(s);
+}
+
 #if defined(_SEQUENT_) && !defined(NAMEDPIPE)
 #undef connect
 /*
@@ -1590,12 +1634,16 @@ struct msg *mp;
   if (fc != fullcmd)
     *--fc = 0;
   if (Parse(fullcmd, fc - fullcmd, args, argl) <= 0)
-    return;
+    {
+      /* XXX: Return some useful message back if MSG_QUERY */
+      return;
+    }
 #ifdef MULTIUSER
   user = *FindUserPtr(mp->m.attach.auser);
   if (user == 0)
     {
       Msg(0, "Unknown user %s tried to send a command!", mp->m.attach.auser);
+      /* XXX: Return some useful message back if MSG_QUERY */
       return;
     }
 #else
@@ -1605,6 +1653,7 @@ struct msg *mp;
   if (user->u_password && *user->u_password)
     {
       Msg(0, "User %s has a password, cannot use -X option.", mp->m.attach.auser);
+      /* XXX: Return some useful message back if MSG_QUERY */
       return;
     }
 #endif