Os Library Tutorial

wiki

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])

TODO: Describe: 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