io.lines ([filename, ···]) Opens the given file name in read mode and returns an iterator function that works like file:lines(···) over the opened file. When the iterator function detects the end of file, it returns no values (to finish the loop) and automatically closes the file. The call io.lines() (with no file name) is equivalent to io.input():lines("*l"); that is, it iterates over the lines of the default input file. In this case it does not close the file when the loop ends. In case

io.open (filename [, mode]) This function opens a file, in the mode specified in the string mode. In case of success, it returns a new file handle. The mode string can be any of the following: "r": read mode (the default); "w": write mode; "a": append mode; "r+": update mode, all previous data is preserved; "w+": update mode, all previous data is erased; "a+": append update mode, previous data is preserved, writing is only allowed at the end of file. The mode string can also

io.output ([file]) Similar to io.input, but operates over the default output file.

io.popen (prog [, mode]) This function is system dependent and is not available on all platforms. Starts program prog in a separated process and returns a file handle that you can use to read data from this program (if mode is "r", the default) or to write data to this program (if mode is "w").

io.read (···) Equivalent to io.input():read(···).

io.tmpfile () In case of success, returns a handle for a temporary file. This file is opened in update mode and it is automatically removed when the program ends.

io.type (obj) Checks whether obj is a valid file handle. Returns the string "file" if obj is an open file handle, "closed file" if obj is a closed file handle, or nil if obj is not a file handle.

io.write (···) Equivalent to io.output():write(···).

ipairs (t) Returns three values (an iterator function, the table t, and 0) so that the construction for i,v in ipairs(t) do body end will iterate over the key–value pairs (1,t[1]), (2,t[2]), ..., up to the first nil value.

load (chunk [, chunkname [, mode [, env]]]) Loads a chunk. If chunk is a string, the chunk is this string. If chunk is a function, load calls it repeatedly to get the chunk pieces. Each call to chunk must return a string that concatenates with previous results. A return of an empty string, nil, or no value signals the end of the chunk. If there are no syntactic errors, returns the compiled chunk as a function; otherwise, returns nil plus the error message. If the resulting function has