Index: builtins.c
===================================================================
--- builtins.c	(revision 77091)
+++ builtins.c	(working copy)
@@ -2234,13 +2234,31 @@
     }
 #endif
 
+/* should this be moved to strings module? */
+static void string_rtrim( string * s )
+{
+    unsigned long len = s->size;
+    while ( len > 0 && isspace( s->value[len-1] ) )
+        --len;
+    if ( len < s->size )
+        string_truncate( s, len );
+}
 
-static char * rtrim( char * s )
+/* should this be moved to strings module? */
+static void string_char_replace( string * s, char fr, char to )
 {
-    char * p = s;
-    while ( *p ) ++p;
-    for ( --p; p >= s && isspace( *p ); *p-- = 0 );
-    return s;
+    char * p = s->value;
+    for ( ; *p ; ++p )
+    {
+        if ( *p == fr )
+            *p = to;
+    }
+    if ( to == 0 ) /* possible truncation */
+    {
+        int len = strlen( s->value );
+        if ( len < s->size )
+            string_truncate( s, len );
+    }
 }
 
 LIST * builtin_shell( FRAME * frame, int flags )
@@ -2255,6 +2273,7 @@
     int      exit_status_opt = 0;
     int      no_output_opt = 0;
     int      strip_eol_opt = 0;
+    int      join_lines_opt = 0;
 
     /* Process the variable args options. */
     {
@@ -2274,6 +2293,10 @@
             {
                 strip_eol_opt = 1;
             }
+            else if ( strcmp("join-lines", object_str( arg->value ) ) == 0 )
+            {
+                join_lines_opt = 1;
+            }
             arg = lol_get( frame->args, ++a );
         }
     }
@@ -2294,12 +2317,12 @@
     {
         buffer[ret] = 0;
         if ( !no_output_opt )
-        {
-            if ( strip_eol_opt )
-                rtrim(buffer);
             string_append( &s, buffer );
-        }
     }
+    if ( join_lines_opt )
+        string_char_replace( &s, '\n', ' ' );
+    else if ( strip_eol_opt )
+        string_rtrim( &s );
 
     exit_status = pclose( p );