diff --git a/nselib/asn1.lua b/nselib/asn1.lua
index 8fa33416f..45780c53e 100644
--- a/nselib/asn1.lua
+++ b/nselib/asn1.lua
@@ -272,7 +272,7 @@ ASN1Encoder = {
 	---
 	-- Encodes an ASN1 sequence
 	encodeSeq = function(self, seqData)
-		return bin.pack('HAA' , '30', self.encodeLength(string.len(seqData)), seqData)
+		return bin.pack('HAA' , '30', self.encodeLength(#seqData), seqData)
 	end,
 
 	---
@@ -318,13 +318,13 @@ ASN1Encoder = {
 		-- Integer encoder
 		self.encoder['number'] = function( self, val )
 			local ival = self.encodeInt(val)
-	  		local len = self.encodeLength(string.len(ival))
+	  		local len = self.encodeLength(#ival)
 	  		return bin.pack('HAA', '02', len, ival)
 		end
 
 		-- Octet String encoder
 		self.encoder['string'] = function( self, val )
-			local len = self.encodeLength(string.len(val))
+			local len = self.encodeLength(#val)
 			return bin.pack('HAA', '04', len, val)
 		end
 
diff --git a/nselib/base64.lua b/nselib/base64.lua
index 065773ffb..bef7eceb9 100644
--- a/nselib/base64.lua
+++ b/nselib/base64.lua
@@ -163,7 +163,7 @@ function dec(b64data)
 	local pos = 1
 	local byte
 	local nbyte = ''
-	for pos = 1, #b64data do -- while pos <= string.len(b64data) do
+	for pos = 1, #b64data do -- while pos <= #b64data do
 		byte = b64dec6bit(substr(b64data, pos, pos))
 		if not byte then return end
 		nbyte = nbyte .. byte
diff --git a/nselib/dns.lua b/nselib/dns.lua
index 8df8180b9..7dc1b1a90 100644
--- a/nselib/dns.lua
+++ b/nselib/dns.lua
@@ -336,7 +336,7 @@ function reverse(ip)
         -- padding
         local mask = "0000"
         for i, part in ipairs(ipParts) do
-             ipParts[i] = mask:sub(1, string.len(mask) - string.len(part)) .. part
+             ipParts[i] = mask:sub(1, #mask - #part) .. part
         end
         -- 32 parts from 8
         local temp = {}
diff --git a/nselib/http.lua b/nselib/http.lua
index df89c0e9a..32038eacd 100644
--- a/nselib/http.lua
+++ b/nselib/http.lua
@@ -1461,12 +1461,12 @@ local function read_quoted_string(s, pos)
   end
   pos = pos + 1
   pos = skip_space(s, pos)
-  while pos <= string.len(s) and string.sub(s, pos, pos) ~= "\"" do
+  while pos <= #s and string.sub(s, pos, pos) ~= "\"" do
     local c
 
     c = string.sub(s, pos, pos)
     if c == "\\" then
-      if pos < string.len(s) then
+      if pos < #s then
         pos = pos + 1
         c = string.sub(s, pos, pos)
       else
@@ -1477,7 +1477,7 @@ local function read_quoted_string(s, pos)
     chars[#chars + 1] = c
     pos = pos + 1
   end
-  if pos > string.len(s) or string.sub(s, pos, pos) ~= "\"" then
+  if pos > #s or string.sub(s, pos, pos) ~= "\"" then
     return nil
   end
 
@@ -1561,7 +1561,7 @@ local function read_auth_challenge(s, pos)
 
   params = {}
   pos = skip_space(s, pos)
-  while pos < string.len(s) do
+  while pos < #s do
     local name, val
     local tmp_pos
 
@@ -1595,7 +1595,7 @@ local function read_auth_challenge(s, pos)
     pos = skip_space(s, pos)
     if string.sub(s, pos, pos) == "," then
       pos = skip_space(s, pos + 1)
-      if pos > string.len(s) then
+      if pos > #s then
         return nil
       end
     end
@@ -1615,7 +1615,7 @@ function parse_www_authenticate(s)
   local pos
 
   pos = 1
-  while pos <= string.len(s) do
+  while pos <= #s do
     local challenge
 
     pos, challenge = read_auth_challenge(s, pos)
@@ -1696,7 +1696,7 @@ function can_use_head(host, port, result_404, path)
 
     if data.status and data.status == 200 and data.header then
       -- check that a body wasn't returned
-      if string.len(data.body) > 0 then
+      if #data.body > 0 then
         stdnse.print_debug(1, "HTTP: Warning: Host returned data when performing HEAD.")
         return false
       end
@@ -1892,7 +1892,7 @@ function page_exists(data, result_404, known_404, page, displayall)
     if(data.status == 200) then
       if(result_404 == 200) then
         -- If the 404 response is also "200", deal with it (check if the body matches)
-        if(string.len(data.body) == 0) then
+        if(#data.body == 0) then
           -- I observed one server that returned a blank string instead of an error, on some occasions
           stdnse.print_debug(1, "HTTP: Page returned a totally empty body; page likely doesn't exist")
           return false
diff --git a/nselib/ipOps.lua b/nselib/ipOps.lua
index 3859d9b63..31befc361 100644
--- a/nselib/ipOps.lua
+++ b/nselib/ipOps.lua
@@ -248,7 +248,7 @@ compare_ip = function( left, op, right )
     return nil, table.concat( err, " " )
   end
 
-  if string.len( left ) ~= string.len( right ) then
+  if # left  ~= # right  then
       -- shouldn't happen...
       return nil, "Error in ipOps.compare_ip: Binary IP addresses were of different lengths."
   end
@@ -262,7 +262,7 @@ compare_ip = function( left, op, right )
 
   -- starting from the leftmost bit, subtract the bit in right from the bit in left
   local compare
-  for i = 1, string.len( left ), 1 do
+  for i = 1, # left , 1 do
     compare = tonumber( string.sub( left, i, i ) ) - tonumber( string.sub( right, i, i ) )
     if compare == 1 then
       return true
@@ -485,7 +485,7 @@ get_last_ip = function( ip, prefix )
   if err then return nil, err end
 
   prefix = tonumber( prefix )
-  if not prefix or ( prefix < 0 ) or ( prefix > string.len( first ) ) then
+  if not prefix or ( prefix < 0 ) or ( prefix > # first  ) then
     return nil, "Error in ipOps.get_last_ip: Invalid prefix length."
   end
 
@@ -534,7 +534,7 @@ ip_to_bin = function( ip )
 
   -- padding
   for i, v in ipairs( t ) do
-    t[i] = mask:sub( 1, string.len( mask ) - string.len( v ) ) .. v
+    t[i] = mask:sub( 1, # mask  - # v  ) .. v
   end
 
   return hex_to_bin( table.concat( t ) )
@@ -559,9 +559,9 @@ bin_to_ip = function( binstring )
   end
 
   local af
-  if string.len( binstring ) == 32 then
+  if # binstring  == 32 then
     af = 4
-  elseif string.len( binstring ) == 128 then
+  elseif # binstring  == 128 then
     af = 6
   else
     return nil, "Error in ipOps.bin_to_ip: Expected exactly 32 or 128 binary digits."
@@ -609,7 +609,7 @@ hex_to_bin = function( hex )
   local t, mask, binchar = {}, "0000"
   for hexchar in string.gmatch( hex, "%x" ) do
       binchar = stdnse.tobinary( tonumber( hexchar, 16 ) )
-      t[#t+1] = mask:sub( 1, string.len( mask ) - string.len( binchar ) ) .. binchar
+      t[#t+1] = mask:sub( 1, # mask  - # binchar  ) .. binchar
   end
   return table.concat( t )
 
diff --git a/nselib/ldap.lua b/nselib/ldap.lua
index 055fc915f..99a937c48 100644
--- a/nselib/ldap.lua
+++ b/nselib/ldap.lua
@@ -76,15 +76,15 @@ local tagEncoder = {}
 tagEncoder['table'] = function(self, val)
 	if (val._ldap == '0A') then
 		local ival = self.encodeInt(val[1])
-		local len = self.encodeLength(string.len(ival))
+		local len = self.encodeLength(#ival)
 		return bin.pack('HAA', '0A', len, ival)	
 	end
 	if (val._ldaptype) then
 		local len
-		if val[1] == nil or string.len(val[1]) == 0 then
+		if val[1] == nil or #val[1] == 0 then
 			return bin.pack('HC', val._ldaptype, 0)
 		else
-			len = self.encodeLength(string.len(val[1]))
+			len = self.encodeLength(#val[1])
 			return bin.pack('HAA', val._ldaptype, len, val[1])
 		end
 	end
@@ -97,7 +97,7 @@ tagEncoder['table'] = function(self, val)
   	if (val["_snmp"]) then 
  		tableType = bin.pack("H", val["_snmp"]) 
   	end
-  	return bin.pack('AAA', tableType, self.encodeLength(string.len(encVal)), encVal)
+  	return bin.pack('AAA', tableType, self.encodeLength(#encVal), encVal)
  	
 end
 
diff --git a/nselib/match.lua b/nselib/match.lua
index 39d90b1d7..0224724cd 100644
--- a/nselib/match.lua
+++ b/nselib/match.lua
@@ -47,7 +47,7 @@ end
 numbytes = function(num)
 	local n = num
 	return function(buf)
-		if(string.len(buf) >=n) then
+		if(#buf >=n) then
 			return n, n
 		end
 		return nil
diff --git a/nselib/mongodb.lua b/nselib/mongodb.lua
index 1a0c15a75..b867847b1 100644
--- a/nselib/mongodb.lua
+++ b/nselib/mongodb.lua
@@ -113,7 +113,7 @@ function toBson(dict)
 		end
 	end
 	-- Get length
-	local length = string.len(elements) + 5
+	local length = #elements + 5
 	
 	if length > 4 * 1024 * 1024 then
 		return false, "document too large - BSON documents are limited to 4 MB"
@@ -563,7 +563,7 @@ function query(socket, data)
 	end
 	
 	local bsonData = responseHeader["bson"]
-	if string.len(bsonData) == 0 then 
+	if #bsonData == 0 then 
 		dbg("No BSon data returned ")
 		return false, "No Bson data returned"
 	end
@@ -626,7 +626,7 @@ function test()
 	local res
 	res = versionQuery()
 	print(type(res),res:len(),res)
-	local  out= bin.unpack('C'..string.len(res),res)
+	local  out= bin.unpack('C'..#res,res)
 	printBuffer(res)
 end
 --test()
diff --git a/nselib/msrpc.lua b/nselib/msrpc.lua
index a51477739..a0b40981d 100644
--- a/nselib/msrpc.lua
+++ b/nselib/msrpc.lua
@@ -309,7 +309,7 @@ function call_function(smbstate, opnum, arguments)
 				0x00,        -- Packet type (0x00 = request)
 				0x03,        -- Packet flags (0x03 = first frag + last frag)
 				0x10000000,  -- Data representation (big endian)
-				0x18 + string.len(arguments), -- Frag length (0x18 = the size of this data)
+				0x18 + #arguments, -- Frag length (0x18 = the size of this data)
 				0x0000,      -- Auth length
 				0x41414141,  -- Call ID (I use 'AAAA' because it's easy to recognize)
 				0x00000038,  -- Alloc hint
@@ -318,7 +318,7 @@ function call_function(smbstate, opnum, arguments)
 				arguments
 			)
 
-	stdnse.print_debug(3, "MSRPC: Calling function 0x%02x with %d bytes of arguments", string.len(arguments), opnum)
+	stdnse.print_debug(3, "MSRPC: Calling function 0x%02x with %d bytes of arguments", #arguments, opnum)
 
 	-- Pass the information up to the smb layer
 	status, result = smb.write_file(smbstate, data, 0)
@@ -391,7 +391,7 @@ function call_function(smbstate, opnum, arguments)
 
 	result['arguments'] = arguments
 
-	stdnse.print_debug(3, "MSRPC: Function call successful, %d bytes of returned argumenst", string.len(result['arguments']))
+	stdnse.print_debug(3, "MSRPC: Function call successful, %d bytes of returned argumenst", #result['arguments'])
 
 	return true, result
 end
@@ -4462,7 +4462,7 @@ RRAS_Opnums["RasRpcGetVersion"] = 15
 function RRAS_SubmitRequest(smbstate, pReqBuffer, dwcbBufSize)
 	--sanity check
 	if(dwcbBufSize == nil) then
-		dwcbBufSize = string.len(pReqBuffer)
+		dwcbBufSize = #pReqBuffer
 	end
 	--pack the request
 	local req_blob
@@ -4581,9 +4581,9 @@ function DNSSERVER_Query(smbstate, server_name, zone, operation)
 	srv_name_utf16 = msrpctypes.string_to_unicode(server_name, true)
 	req_blob = bin.pack("<IIIIAA",
 		unique_ptr,
-		string.len(srv_name_utf16)/2,
+		#srv_name_utf16/2,
 		0,
-		string.len(srv_name_utf16)/2,
+		#srv_name_utf16/2,
 		srv_name_utf16,
 		get_pad(srv_name_utf16, 4))
 	--[in, unique, string] LPCSTR pszZone,
@@ -4593,9 +4593,9 @@ function DNSSERVER_Query(smbstate, server_name, zone, operation)
 		zone_ascii = zone .. string.char(0x00)
 		req_blob = req_blob .. bin.pack("<IIIIAA",
 			unique_ptr + 1,
-			string.len(zone_ascii),
+			#zone_ascii,
 			0,
-			string.len(zone_ascii),
+			#zone_ascii,
 			zone_ascii,
 			get_pad(zone_ascii, 4))
 	end
@@ -4603,9 +4603,9 @@ function DNSSERVER_Query(smbstate, server_name, zone, operation)
   	operation_ascii = operation .. string.char(0x00)
 	req_blob = req_blob .. bin.pack("<IIIIAA",
 		unique_ptr+2,
-		string.len(operation_ascii),
+		#operation_ascii,
 		0,
-		string.len(operation_ascii),
+		#operation_ascii,
 		operation_ascii,
 		get_pad(operation_ascii, 4))
 
@@ -4652,7 +4652,7 @@ end
 --####################################################################--
 function get_pad(data, align, pad_byte)
 	pad_byte = pad_byte or "\00"
-	return string.rep(pad_byte, (align-string.len(data)%align)%align)
+	return string.rep(pad_byte, (align-#data%align)%align)
 end
 
 --####################################################################--
diff --git a/nselib/msrpctypes.lua b/nselib/msrpctypes.lua
index 6f4495f08..568f91680 100644
--- a/nselib/msrpctypes.lua
+++ b/nselib/msrpctypes.lua
@@ -142,7 +142,7 @@ function string_to_unicode(string, do_null)
 		
 
 	-- Loop through the string, adding each character followed by a char(0)
-	for i = 1, string.len(string), 1 do
+	for i = 1, #string, 1 do
 		result = result .. string.sub(string, i, i) .. string.char(0)
 	end
 
@@ -152,7 +152,7 @@ function string_to_unicode(string, do_null)
 	end
 
 	-- Align it to a multiple of 4, if necessary
-	if(string.len(result) % 4 ~= 0) then
+	if(#result % 4 ~= 0) then
 		result = result .. string.char(0) .. string.char(0)
 	end
 
@@ -549,9 +549,9 @@ function marshall_unicode(str, do_null, max_length)
 	end
 
 	if(do_null) then
-		buffer_length = string.len(str) + 1
+		buffer_length = #str + 1
 	else
-		buffer_length = string.len(str)
+		buffer_length = #str
 	end
 
 	if(max_length == nil) then
@@ -580,13 +580,13 @@ function marshall_ascii(str, max_length)
 	local result
 	local padding = ""
 
-	buffer_length = string.len(str) + 1
+	buffer_length = #str + 1
 
 	if(max_length == nil) then
 		max_length = buffer_length
 	end
 
-	while((string.len(str .. string.char(0) .. padding) % 4) ~= 0) do
+	while((#(str .. string.char(0 .. padding)) % 4) ~= 0) do
 		padding = padding .. string.char(0)
 	end
 
@@ -1654,14 +1654,14 @@ local function marshall_lsa_String_internal(location, str, max_length, do_null)
 		if(str == nil) then
 			max_length = 0
 		else
-			max_length = string.len(str)
+			max_length = #str
 		end
 	end
 
 	if(str == nil) then
 		length = 0
 	else
-		length = string.len(str)
+		length = #str
 	end
 
 	if(do_null == nil) then
@@ -2685,7 +2685,7 @@ function marshall_winreg_StringBuf(table, max_length)
 		if(name == nil) then
 			max_length = 0
 		else
-			max_length = string.len(name) + 1
+			max_length = #name + 1
 		end
 	end
 
@@ -2697,7 +2697,7 @@ function marshall_winreg_StringBuf(table, max_length)
 		if(name == nil) then
 			length = 0
 		else
-			length = string.len(name) + 1
+			length = #name + 1
 		end
 
 		result = bin.pack("<SSA", length * 2, max_length * 2, marshall_ptr(ALL, marshall_unicode, {name, true, max_length}, name))
diff --git a/nselib/netbios.lua b/nselib/netbios.lua
index 7e47f2e75..f0dd7c0f8 100644
--- a/nselib/netbios.lua
+++ b/nselib/netbios.lua
@@ -31,7 +31,7 @@ function name_encode(name, scope)
 
 	stdnse.print_debug(3, "Encoding name '%s'", name)
 	-- Truncate or pad the string to 16 bytes
-	if(string.len(name) >= 16) then
+	if(#name >= 16) then
 		name = string.sub(name, 1, 16)
 	else
 		local padding = " "
@@ -41,7 +41,7 @@ function name_encode(name, scope)
 
 		repeat
 			name = name .. padding
-		until string.len(name) == 16
+		until #name == 16
 	end
 
 	-- Convert to uppercase
@@ -49,7 +49,7 @@ function name_encode(name, scope)
 
 	-- Do the L1 encoding
 	local L1_encoded = ""
-	for i=1, string.len(name), 1 do
+	for i=1, #name, 1 do
 		local b = string.byte(name, i)
 		L1_encoded = L1_encoded .. string.char(bit.rshift(bit.band(b, 0xF0), 4) + 0x41)
 		L1_encoded = L1_encoded .. string.char(bit.rshift(bit.band(b, 0x0F), 0) + 0x41)
@@ -62,7 +62,7 @@ function name_encode(name, scope)
 		-- Split the scope at its periods
 		local piece
 		for piece in string.gmatch(scope, "[^.]+") do
-			L2_encoded = L2_encoded .. string.char(string.len(piece)) .. piece
+			L2_encoded = L2_encoded .. string.char(#piece) .. piece
 		end
 	end
 
@@ -97,15 +97,15 @@ function name_decode(encoded_name)
 
 	-- Decode the scope
 	local pos = 34
-	while string.len(encoded_name) > pos do
+	while #encoded_name > pos do
 		local len = string.byte(encoded_name, pos)
 		scope = scope .. string.sub(encoded_name, pos + 1, pos + len) .. "."
 		pos = pos + 1 + len
 	end
 
 	-- If there was a scope, remove the trailing period
-	if(string.len(scope) > 0) then
-		scope = string.sub(scope, 1, string.len(scope) - 1)
+	if(#scope > 0) then
+		scope = string.sub(scope, 1, #scope - 1)
 	end
 
 	stdnse.print_debug(3, "=> '%s'", name)
diff --git a/nselib/nsedebug.lua b/nselib/nsedebug.lua
index 9f1f08db7..37f9edf29 100644
--- a/nselib/nsedebug.lua
+++ b/nselib/nsedebug.lua
@@ -62,7 +62,7 @@ end
 function print_hex(str)
 
 	-- Prints out the full lines
-	for line=1, string.len(str)/16, 1 do
+	for line=1, #str/16, 1 do
 		io.write(string.format("%08x ", (line - 1) * 16))
 
 		-- Loop through the string, printing the hex
@@ -86,17 +86,17 @@ function print_hex(str)
 	end
 
 	-- Prints out the final, partial line
-	local line = math.floor((string.len(str)/16)) + 1
+	local line = math.floor((#str/16)) + 1
 	io.write(string.format("%08x ", (line - 1) * 16))
 
-	for char=1, string.len(str) % 16, 1 do
+	for char=1, #str % 16, 1 do
 		local ch = string.byte(str, ((line - 1) * 16) + char)
 		io.write(string.format("%02x ", ch))
 	end
-	io.write(string.rep("   ", 16 - (string.len(str) % 16)));
+	io.write(string.rep("   ", 16 - (#str % 16)));
 	io.write("   ")
 
-	for char=1, string.len(str) % 16, 1 do
+	for char=1, #str % 16, 1 do
 		local ch = string.byte(str, ((line - 1) * 16) + char)
 		if ch < 0x20 or ch > 0x7f then
 			ch = string.byte(".", 1)
@@ -105,7 +105,7 @@ function print_hex(str)
 	end
 
 	-- Print out the length
-	io.write(string.format("\n         Length: %d [0x%x]\n", string.len(str), string.len(str)))
+	io.write(string.format("\n         Length: %d [0x%x]\n", #str, #str))
 
 end
 
diff --git a/nselib/packet.lua b/nselib/packet.lua
index 9e2025366..a27bbc7a3 100644
--- a/nselib/packet.lua
+++ b/nselib/packet.lua
@@ -128,7 +128,7 @@ Packet = {}
 --- Create a new Packet object.
 -- @param packet Binary string with packet data.
 -- @param packet_len Packet length. It could be more than
--- <code>string.len(packet)</code>.
+-- <code>#packet</code>.
 -- @param force_continue whether an error in parsing headers should be fatal or
 -- not. This is especially useful when parsing ICMP packets, where a small ICMP
 -- payload could be a TCP header. The problem is that parsing this payload
@@ -236,7 +236,7 @@ end
 -- @return Whether the parsing succeeded.
 function Packet:ip_parse(force_continue)
 	self.ip_offset		= 0
-	if    string.len(self.buf) < 20 then 	-- too short
+	if    #self.buf < 20 then 	-- too short
 		return false
 	end
 	self.ip_v		= bit.rshift(bit.band(self:u8(self.ip_offset + 0), 0xF0), 4)
@@ -391,7 +391,7 @@ end
 -- @return Whether the parsing succeeded.
 function Packet:icmp_parse(force_continue)
 	self.icmp_offset	= self.ip_data_offset
-	if string.len(self.buf) < self.icmp_offset + 8 then -- let's say 8 bytes minimum
+	if #self.buf < self.icmp_offset + 8 then -- let's say 8 bytes minimum
 		return false
 	end
 	self.icmp = true
@@ -403,7 +403,7 @@ function Packet:icmp_parse(force_continue)
 		self.icmp_payload = true
 		self.icmp_r0	  = self:u32(self.icmp_offset + 4)
 		self.icmp_payload_offset = self.icmp_offset + 8
-		if string.len(self.buf) < self.icmp_payload_offset + 24 then
+		if #self.buf < self.icmp_payload_offset + 24 then
 			return false
 		end
 		self.icmp_payload = Packet:new(self.buf:sub(self.icmp_payload_offset+1), self.packet_len - self.icmp_payload_offset, true)
@@ -423,12 +423,12 @@ end
 function Packet:tcp_parse(force_continue)
 	self.tcp = true
 	self.tcp_offset		= self.ip_data_offset
-	if string.len(self.buf) < self.tcp_offset + 4 then
+	if #self.buf < self.tcp_offset + 4 then
 		return false
 	end
 	self.tcp_sport		= self:u16(self.tcp_offset + 0)
 	self.tcp_dport		= self:u16(self.tcp_offset + 2)
-	if string.len(self.buf) < self.tcp_offset + 20 then
+	if #self.buf < self.tcp_offset + 20 then
 		if force_continue then
 			return true
 		else
@@ -609,12 +609,12 @@ end
 function Packet:udp_parse(force_continue)
 	self.udp = true
 	self.udp_offset		= self.ip_data_offset
-	if string.len(self.buf) < self.udp_offset + 4 then
+	if #self.buf < self.udp_offset + 4 then
 		return false
 	end
 	self.udp_sport		= self:u16(self.udp_offset + 0)
 	self.udp_dport		= self:u16(self.udp_offset + 2)
-	if string.len(self.buf) < self.udp_offset + 8 then
+	if #self.buf < self.udp_offset + 8 then
 		if force_continue then
 			return true
 		else
diff --git a/nselib/smb.lua b/nselib/smb.lua
index 4c74ed20e..38e71e013 100644
--- a/nselib/smb.lua
+++ b/nselib/smb.lua
@@ -670,7 +670,7 @@ local function smb_encode_parameters(parameters, overrides)
 	-- Make sure we have an overrides array
 	overrides = overrides or {}
 	
-	return bin.pack("<CA", (overrides['parameters_length'] or (string.len(parameters) / 2)), parameters)
+	return bin.pack("<CA", (overrides['parameters_length'] or (#parameters / 2)), parameters)
 end
 
 --- Converts a string containing the data section into the encoded data string. 
@@ -686,7 +686,7 @@ local function smb_encode_data(data, overrides)
 	-- Make sure we have an overrides array
 	overrides = overrides or {}
 
-	return bin.pack("<SA", (overrides['data_length'] or string.len(data)), data)
+	return bin.pack("<SA", (overrides['data_length'] or #data), data)
 end
 
 ---Sign the message, if possible. This is done by replacing the signature with the sequence
@@ -774,12 +774,12 @@ function smb_send(smb, header, parameters, data, overrides)
 	-- Calculate the message signature
 	body = message_sign(smb, body)
 
-    local out = bin.pack(">I<A", string.len(body), body)
+    local out = bin.pack(">I<A", #body, body)
 
 
 	repeat
 		attempts = attempts - 1
-		stdnse.print_debug(3, "SMB: Sending SMB packet (len: %d, attempts remaining: %d)", string.len(out), attempts)
+		stdnse.print_debug(3, "SMB: Sending SMB packet (len: %d, attempts remaining: %d)", #out, attempts)
 		status, err = smb['socket']:send(out)
 	until(status or (attempts == 0))
 
@@ -899,7 +899,7 @@ function smb_read(smb, read_data)
 		data = nil
 	end
 
-	stdnse.print_debug(3, "SMB: Received %d bytes", string.len(result))
+	stdnse.print_debug(3, "SMB: Received %d bytes", #result)
 	return true, header, parameters, data
 end
 
@@ -1650,7 +1650,7 @@ function create_file(smb, path, overrides)
 						0x00,   -- ANDX reserved
 						0x0000, -- ANDX offset
 						0x00,   -- Reserved
-						string.len(path), -- Path length
+						#path, -- Path length
 						(overrides['file_create_flags']            or 0x00000016),         -- Create flags
 						(overrides['file_create_root_fid']         or 0x00000000),         -- Root FID
 						(overrides['file_create_access_mask']      or 0x02000000),         -- Access mask
@@ -2106,9 +2106,9 @@ function send_transaction_named_pipe(smb, function_parameters, function_data, pi
 
 	-- Convert the parameter/data offsets into something more useful (the offset into the data section)
 	-- - 0x20 for the header, - 0x01 for the length. 
-	parameter_offset = parameter_offset - 0x20 - 0x01 - string.len(parameters) - 0x02;
+	parameter_offset = parameter_offset - 0x20 - 0x01 - #parameters - 0x02;
 	-- - 0x20 for the header, - 0x01 for parameter length, the parameter length, and - 0x02 for the data length. 
-	data_offset = data_offset - 0x20 - 0x01 - string.len(parameters) - 0x02;
+	data_offset = data_offset - 0x20 - 0x01 - #parameters - 0x02;
 
 	-- I'm not sure I entirely understand why the '+1' is here, but I think it has to do with the string starting at '1' and not '0'.
 	function_parameters = string.sub(data, parameter_offset + 1, parameter_offset + parameter_count)
diff --git a/nselib/snmp.lua b/nselib/snmp.lua
index 1ff6c6d63..58a21159b 100644
--- a/nselib/snmp.lua
+++ b/nselib/snmp.lua
@@ -34,7 +34,7 @@ tagEncoder['table'] = function(self, val)
     -- counter or gauge or timeticks or opaque
 	elseif (val._snmp == '41' or val._snmp == '42' or val._snmp == '43' or val._snmp == '44') then
 		local val = self:encodeInt(val[1])
-		return bin.pack("HAA", val._snmp, self.encodeLength(string.len(val)), val)
+		return bin.pack("HAA", val._snmp, self.encodeLength(#val), val)
 	end
 	
 	local encVal = ""
@@ -46,7 +46,7 @@ tagEncoder['table'] = function(self, val)
 	if (val["_snmp"]) then 
 		tableType = bin.pack("H", val["_snmp"]) 
 	end
-	return bin.pack('AAA', tableType, self.encodeLength(string.len(encVal)), encVal)
+	return bin.pack('AAA', tableType, self.encodeLength(#encVal), encVal)
 end
 
 ---
diff --git a/nselib/tab.lua b/nselib/tab.lua
index b0a0bf3dc..284679503 100644
--- a/nselib/tab.lua
+++ b/nselib/tab.lua
@@ -96,7 +96,7 @@ function dump(t)
 	for i, row in ipairs(t) do
 		num_columns[i] = 0
 		for x, elem in pairs(row) do
-			local elem_width = string.len(elem)
+			local elem_width = #elem
 			if not column_width[x] or elem_width > column_width[x] then
 				column_width[x] = elem_width
 			end
diff --git a/nselib/url.lua b/nselib/url.lua
index 1c3dfa025..96a39f39d 100644
--- a/nselib/url.lua
+++ b/nselib/url.lua
@@ -350,5 +350,5 @@ function build_query(query)
 	for i,v in pairs(query) do 
 		qstr = qstr .. i .. '=' .. v .. '&'
 	end
-	return string.sub(qstr, 0, string.len(qstr)-1)
+	return string.sub(qstr, 0, #qstr-1)
 end