direct errors to separate file

SL.jl

@@ -176,6 +176,8 @@ function parse_commandline()
 end
 
 function main()
+
+
     parsed_args = parse_commandline()
 
     # SL(3,Z)
@@ -205,6 +207,20 @@ function main()
     end
     name = name*"-$(string(upper_bound))"
 
+    (errorRead, errorWrite) = redirect_stderr()
+    atexit(function ()
+        close(errorWrite)
+
+        errors = readavailable(errorRead)
+
+        close(errorRead)
+        if size(errors) > 0
+            open("$(name)/errors.log", "a") do io
+                write(io, errors)
+            end
+        end
+    end)
+
     S() = SL_generatingset(N, p)
 
     if parsed_args["cpus"] ≠ nothing