)
Calls the C function exit, with an optional code, to terminate the host program. The default value for code is the success code.
os.getenv (varname)
Returns the value of the process environment variable varname, or nil if the variable is not defined.
os.remove (filename)
Deletes the file with the given name. If this function fails, it returns nil, plus a string describing the error.
os.rename (oldname, newname)
Renames file named oldname to newname. If this function fails, it returns nil, plus a string describing the error.
os.setlocale (locale [, category])
Sets the current locale of the program. locale is a string specifying a locale; category is an optional string describing which category to change: "all", "collate", "ctype", "monetary", "numeric", or "time"; the default category is "all". The function returns the name of the new locale, or nil if the request cannot be honored.
os.time ([table])
Returns the current time when called without arguments, or a time representing the date and time specified by the given table. This table must have fields year, month, and day, and may have fields hour, min, sec, and isdst (for a description of these fields, see the os.date function).
The returned value is a number, whose meaning depends on your system. In Posix, Windows, and some other systems, this number counts the number of seconds since some given start time (the "epoch"). In other systems, the meaning is not specified, and the number returned by time can be used only as an argument to date and difftime.
os.tmpname ()
Returns a string with a file name that can be used for a temporary file. The file must be explicitly opened before its use and removed when no longer needed.
This function is equivalent to the tmpnam C function, and many people (and even some compilers!) advise against its use, because between the time you call this function and the time you open the file, it is possible for another process to create a file with the same name.