ed: standard exit code (#863)

* When running an ed script the exit code is important
* If any command in the script fails, edWarn() will be called and $Error will be set; this should translate to a failure exit code
* Tested against GNU version

#test1: q command after invalid address error
470
*H
*100p
?
invalid address
*10p
	/* this? */
*q
%echo $?
1

#test2: wq command after invalid address error
470
*H
*100p
?
invalid address
*1,2wq new.txt
39
%echo $?
1

bin/ed

@@ -113,7 +113,7 @@ my $NO_QUESTIONS_MODE = 0;
 my $PRINT_NUM = 1;
 my $PRINT_BIN = 2;
 
-our $VERSION = '0.20';
+our $VERSION = '0.21';
 
 my @ESC = (
     '\\000', '\\001', '\\002', '\\003', '\\004', '\\005', '\\006', '\\a',
@@ -275,6 +275,11 @@ sub maxline {
     return $n;
 }
 
+sub getrc {
+    return EX_FAILURE if defined $Error;
+    return EX_SUCCESS;
+}
+
 sub edChangeLines {
     my $err = edDelete();
     unless ($err) {
@@ -646,7 +651,7 @@ sub edWrite {
 
     $NeedToSave = $UserHasBeenWarned = 0;
     print "$chars\n" unless $Scripted;
-    exit EX_SUCCESS if $qflag;
+    exit getrc() if $qflag;
     return;
 }
 
@@ -815,7 +820,7 @@ sub edQuit {
         $UserHasBeenWarned = 1;
         return E_UNSAVED;
     }
-    exit EX_SUCCESS;
+    exit getrc();
 }
 
 #
@@ -1240,6 +1245,16 @@ Display current line number
 
 =back
 
+=head1 EXIT STATUS
+
+=over 4
+
+=item * 0 - All commands were processed successfully
+
+=item * 1 - An error occurred
+
+=back
+
 =head1 AUTHOR
 
 Written by George M Jones