os.outputof: add a second argument to select which stream to output

local o, e = os.outputof(cmd, streams)

    Where streams could be one of
    - "output" Only return standard output stream content
    - "error" Only return standard error stream content
    - "both" (default) Return both streams content

src/base/os.lua

@@ -455,12 +455,25 @@
 
 --
 -- Run a shell command and return the output.
+--
+-- @param cmd Command to execute
+-- @param streams Standard stream(s) to output
+-- 		Must be one of 
+--		- "botn" (default)
+--		- "output" Return standard output stream content only
+--		- "error" Return standard error stream content only
 --
 
-	function os.outputof(cmd)
+	function os.outputof(cmd, streams)
 		cmd = path.normalize(cmd)
+		local redirection = " 2>&1"
+		if streams == "output" then
+			redirection = " 2>/dev/null"
+		elseif streams == "error" then
+			redirection = " 2>&1 1>/dev/null"
+		end
 
-		local pipe = io.popen(cmd .. " 2>&1")
+		local pipe = io.popen(cmd .. redirection)
 		local result = pipe:read('*a')
 		local success, what, code = pipe:close()
 		if success then

tests/base/test_os.lua

@@ -184,8 +184,26 @@
 			end
 		end
 	end
-
+	
-
+	-- Check outputof content
+	function suite.outputof_streams_output()
+		if (os.istarget("macosx")
+			or os.istarget("linux")
+			or os.istarget("solaris")
+			or os.istarget("bsd"))
+			and os.isdir (_TESTS_DIR)
+		then
+			local ob, e = os.outputof ("ls " .. _TESTS_DIR .. "/base")
+			local oo, e = os.outputof ("ls " .. _TESTS_DIR .. "/base", "output")
+			test.isequal (oo, ob)
+			local s, e = string.find (oo, "test_os.lua")
+			test.istrue(s ~= nil)
+			
+			local o, e = os.outputof ("ls " .. cwd .. "/base", "error")
+			test.istrue(o == nil or #o == 0)
+		end
+	end
+	
 --
 -- os.translateCommand() tests
 --