Os Library Tutorial

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os.clock()

Return CPU time since Lua started in seconds.

 > = os.clock() 11056.989 

os.date([format [, time]])

Return formatted date string, or table of time information. The format string has the same format as the C strftime() function.

TODO: insert info, examples and links to strftime()

List all params at http://www.cplusplus.com/reference/clibrary/ctime/strftime/

Simple example:

 > = os.date("%d.%m.%Y") 06.10.2012 

If the format string is "*t" a table is returned containing the time information, e.g,

 > table.foreach(os.date('*t'), print) hour 14 min 36 wday 1 year 2003 yday 124 month 5 sec 33 day 4 isdst true 

Above example using pairs() method:

 > for k, v in pairs(os.date("*t")) do print(k, v) end year 2012 day 1 min 54 wday 4 month 8 isdst true yday 214 sec 39 hour 14 

If the format is preceeded by "!" the time is converted to Coordinated Universal Time, e.g.,

 > table.foreach(os.date('!*t'), print) hour 21 min 36 wday 1 year 2003 yday 124 month 5 sec 42 day 4 isdst false 

Above example using pairs() method:

 > for k, v in pairs(os.date("!*t")) do print(k, v) end year 2012 day 1 min 58 wday 4 month 8 isdst false yday 214 sec 39 hour 12 

os.date() returns a string in the format MM/DD/YY HH:MM:SS.

 > print(os.date()) 08/16/05 10:22:32 

Nowadays os.date() returns a string in different format:

 > = os.date() Wed Aug 1 15:00:47 2012 

os.difftime(t2, t1)

Calculate the number of seconds between time t1 to time t2.

 > t1 = os.time() > -- wait a little while then type.... > = os.difftime(os.time(), t1) 31 > = os.difftime(os.time(), t1) 38 

os.execute([command])

Execute an operating system shell command. This is like the C system() function. The system dependent status code is returned.

 > = os.execute("echo hello") hello 0 > = os.execute("mmmmm") -- generate an error 'mmmmm' is not recognized as an internal or external command, operable program or batch file. 1 

With no argument, this command returns a non-zero value if an OS shell is presents or a zero value if one is not present.

 > = os.execute() -- no argument 1 

os.exit([code])

Calls the C function exit, with an optional code, to terminate the host program. The default value for code is the success code.

 > os.exit(0) -- kill the Lua shell we are in and pass 0 back to parent shell 

os.getenv(varname)

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

 > = os.getenv("BANANA") nil > = os.getenv("USERNAME") Nick 

os.remove(filename)

Deletes the file with the given name. If this function fails, it returns nil, plus a string describing the error.

 > os.execute("echo hello > banana.txt") > = os.remove("banana.txt") true > = os.remove("banana.txt") nil banana.txt: No such file or directory 2 

os.rename(oldname, newname)

Renames file named oldname to newname. If this function fails, it returns nil, plus a string describing the error.

 > os.execute("echo hello > banana.txt") > = os.rename("banana.txt", "apple.txt") true > = os.rename("banana.txt", "apple.txt") nil banana.txt: No such file or directory 2 

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])

Given a formatted date table, as used by os.date() return the time in system seconds.

 > t = os.date('*t') -- time now > table.foreach(os.date('*t'), print) hour 15 min 1 wday 1 year 2003 yday 124 month 5 sec 2 day 4 isdst true > = os.time(t) -- time in system seconds 1052085659 > t.year = 2001 -- 2001, a Lua odyssey > = os.time(t) -- time then 989013659 

os.tmpname ()

Generate a name that can be used for a temporary file. This only generates a name, it does not open a file.

 > = os.tmpname() -- on windows \s2js. 

 > = os.tmpname() -- on debian /tmp/lua_5xPi18