add readme

README.md

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+# LOGFOO
+Filter and format logfiles on command line
+
+## build
+* LUA required ;)
+```
+gcc -I/usr/include/lua5.4 -g logfoo.c -llua5.4 -o logfoo
+```
+
+## usage
+```
+logfoo <path to lua> <path to logfile>
+```
+### lua
+* the lua needs 2 methods
+  * `function filter (line)` returns boolean; true -> don't print line
+  * `function format (line)` returns string
+* example:
+```lua
+function filter (line)
+    -- only lines containing text "Unknown kernel..."
+    return line:find("Unknown kernel command line parameters") == nil
+end
+
+function format (line)
+    -- red, bold, underline text "IMAGE"
+    line = line:gsub("(IMAGE)", color("%1", "31;1;4"))
+    -- green text "gentoo"
+    line = line:gsub("(gentoo)", color("%1", "32"))
+    -- only text between "
+    return line:match("\"([^\"]+)\"")
+end
+```