main.c, add variable 'batchmode'

which is set when command line option `-b' is active

examples/control_structs/if-batchmode.cir

@@ -0,0 +1,31 @@
+use $batchmode
+
+* use $batchmode variable to steer control flow
+*
+* start either with
+*    ngspice -b -r rawfile.raw if-batchmode.cir
+* or with
+*    ngspice if-batchmode.cir
+
+v0  1 0  dc 1
+R1  1 2  1k
+C1  2 0  1u
+
+.tran 100u 10m uic
+.print tran all
+
+.control
+
+if $?batchmode
+  echo "Info: batchmode has been set by command line option -b"
+  echo
+else
+  echo "Info: batchmode has not been set"
+  echo
+  unset ngdebug
+  tran 100u 10m uic
+  plot v(2)
+end
+
+.endc
+.end

src/main.c

@@ -923,8 +923,9 @@ main(int argc, char **argv)
         case 'b':       /* Batch mode */
         {
             bool x_false = FALSE;
+            bool x_true = TRUE;
             cp_vset("addcontrol", CP_BOOL, &x_false);
-
+            cp_vset("batchmode", CP_BOOL, &x_true);
             ft_batchmode = TRUE;
         }
         break;