math.ult()

math.ult (m, n) Returns a boolean, true if and only if integer m is below integer n when they are compared as unsigned integers.

next()

next (table [, index]) Allows a program to traverse all fields of a table. Its first argument is a table and its second argument is an index in this table. next returns the next index of the table and its associated value. When called with nil as its second argument, next returns an initial index and its associated value. When called with the last index, or with nil in an empty table, next returns nil. If the second argument is absent, then it is interpreted as nil. In particular, you can use

os.clock()

os.clock () Returns an approximation of the amount in seconds of CPU time used by the program.

os.date()

os.date ([format [, time]]) Returns a string or a table containing date and time, formatted according to the given string format. If the time argument is present, this is the time to be formatted (see the os.time function for a description of this value). Otherwise, date formats the current time. If format starts with '!', then the date is formatted in Coordinated Universal Time. After this optional character, if format is the string "*t", then date returns a table with the following fiel

os.difftime()

os.difftime (t2, t1) Returns the difference, in seconds, from time t1 to time t2 (where the times are values returned by os.time). In POSIX, Windows, and some other systems, this value is exactly t2-t1.

os.execute()

os.execute ([command]) This function is equivalent to the ISO C function system. It passes command to be executed by an operating system shell. Its first result is true if the command terminated successfully, or nil otherwise. After this first result the function returns a string plus a number, as follows: "exit": the command terminated normally; the following number is the exit status of the command. "signal": the command was terminated by a signal; the following number is the signal t

os.exit()

os.exit ([code [, close]]) Calls the ISO C function exit to terminate the host program. If code is true, the returned status is EXIT_SUCCESS; if code is false, the returned status is EXIT_FAILURE; if code is a number, the returned status is this number. The default value for code is true. If the optional second argument close is true, closes the Lua state before exiting.

os.getenv()

os.getenv (varname) Returns the value of the process environment variable varname, or nil if the variable is not defined.

os.remove()

os.remove (filename) Deletes the file (or empty directory, on POSIX systems) with the given name. If this function fails, it returns nil, plus a string describing the error and the error code. Otherwise, it returns true.

os.rename()

os.rename (oldname, newname) Renames the file or directory named oldname to newname. If this function fails, it returns nil, plus a string describing the error and the error code. Otherwise, it returns true.