Set exit status for --monitor errors (#67).

docs/pv.1

@@ -754,7 +754,8 @@ pv \-\-numeric \-\-format '{"elapsed":%t,"bytes":%b,"rate":%r,"percentage":%{pro
 .\"
 .SH EXIT STATUS
 An exit status of 1 indicates a problem with the \*(lq\fB\-\-remote\fR\*(rq,
-\*(lq\fB\-\-query\fR\*(rq, or \*(lq\fB\-\-pidfile\fR\*(rq options.
+\*(lq\fB\-\-query\fR\*(rq, \*(lq\fB\-\-pidfile\fR\*(rq, or
+\*(lq\fB\-\-monitor\fR\*(rq options.
 .PP
 Any other exit status is a bitmask of the following:
 .TP 5

src/include/pv.h

@@ -29,6 +29,7 @@ extern "C" {
  */
 #define PV_ERROREXIT_REMOTE_OR_PID 1
 #define PV_ERROREXIT_SAF	   1	/* store and forward error */
+#define PV_ERROREXIT_MONITOR	   1	/* monitor mode error */
 #define PV_ERROREXIT_ACCESS        2
 #define PV_ERROREXIT_OUROBOROS     4
 #define PV_ERROREXIT_TRANSITION    8