diff --git a/pdfmml.lua b/pdfmml.lua
index 5997956..58f509b 100755
--- a/pdfmml.lua
+++ b/pdfmml.lua
@@ -3,6 +3,7 @@ require'pdfmml-emulate-node'
 local convert = require'luamml-convert'
 local mappings = require'luamml-legacy-mappings'
 local to_xml = require'luamml-xmlwriter'
+
 convert.register_family(1, mappings.oml)
 convert.register_family(2, mappings.oms)
 convert.register_family(3, mappings.omx)
@@ -10,19 +11,44 @@ convert.register_family(3, mappings.omx)
 local parse_showlists = require'pdfmml-showlists'
 local parse_log = require'pdfmml-logreader'
 
+local attributes = lfs.attributes
+local function try_extensions_(base, extension, ...)
+  if extension == nil then return end
+  local fullname = base .. extension
+  if attributes(fullname, 'mode') == 'file' then
+    return fullname
+  end
+  return try_extensions_(base, ...)
+end
+local function try_extensions(base, ...)
+  if attributes(base, 'mode') == 'file' then return base end
+  return try_extensions_(base, ...)
+end
+
 if #arg < 1 then
-  io.stderr:write(string.format('Usage: %0 {logname} \n', arg[0]))
+  io.stderr:write(string.format('Usage: %s {logname} [{outname}]\n\z
+    If {outname} includes {}, then a separate file is written for every formula with {} replaced by the formula id.\n', arg[0]))
   os.exit(1)
 end
-local math_lists = assert(parse_log(arg[1]))
+local math_lists = assert(parse_log(assert(try_extensions(arg[1], '.tml', '.log'),
+      "Couldn't find input file.")))
 
-local out_stream = arg[2] and arg[2] ~= '-' and assert(io.open(arg[2], 'w')) or io.stdout
+local out_prefix, out_suffix, out_stream
+if not arg[2] or arg[2] == '-' then
+  out_stream = io.stdout
+else
+  local _ _, _, out_prefix, out_suffix = arg[2]:find'^(.*){}(.*)$'
+  if not out_prefix then
+    out_stream = assert(io.open(arg[2], 'w'))
+  end
+end
 for i, block in ipairs(math_lists.groups) do
+  local stream = out_stream or assert(io.open(out_prefix .. tostring(i) .. out_suffix, 'w'))
   block = block[1]
   local parsed = parse_showlists(block, nil, nil, math_lists.marks)
   local style = block.display and 0 or 2
-  out_stream:write(
+  stream:write(
     to_xml(convert.make_root(convert.process(parsed, style), style)), '\n'
   )
+  if not out_stream then stream:close() end
 end
--- if ... then out_stream:close() end -- Don't bother since we terminate anyway