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NAME

os - operating system facilities (standard library)

OVERVIEW

This library is implemented through table os.

REFERENCE

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 *t, then date returns a table with the following fields:

  year (four digits)
  month (1--12)
  day (1--31)
  hour (0--23)
  min (0--59)
  sec (0--61)
  wday (weekday, Sunday is 1)
  yday (day of the year)
  isdst (daylight saving flag, a boolean)

If format is not *t, then date returns the date as a string, formatted according to the same rules as the function strftime.

When called without arguments, date returns a reasonable date and time representation that depends on the host system and on the current locale (that is, os.date() is equivalent to os.date("%c")).

os.difftime

  os.difftime (t2, t1)

Returns the number of seconds from time t1 to time t2. In POSIX, Windows, and some other systems, this value is exactly t2-t1.

os.execute

  os.execute ([command])

This function is equivalent to the function system. It passes command to be executed by an operating system shell. It returns a status code, which is system-dependent. If command is absent, then it returns nonzero if a shell is available and zero otherwise.

os.exit

  os.exit ([code])

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

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 directory with the given name. Directories must be empty to be removed. If this function fails, it returns nil, plus a string describing the error.

os.rename

  os.rename (oldname, newname)

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

os.setlocale

  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.

When called with nil as the first argument, this function only returns the name of the current locale for the given category.

os.time

  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

  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 explicitly removed when no longer needed.

VERSION

This is Lua version 5.1.1.

CREDITS

Lua is developed at Lua.org, a laboratory of the Department of Computer Science of PUC-Rio (the Pontifical Catholic University of Rio de Janeiro in Brazil). For more information about the authors, see http://www.lua.org/authors.html .

LICENSE

Lua is licensed under the terms of the MIT license reproduced below. This means that Lua is free software and can be used for both academic and commercial purposes at absolutely no cost.

For details and rationale, see http://www.lua.org/license.html .

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Copyright (C) 1994-2006 Lua.org, PUC-Rio.

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The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED ``AS IS'', WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

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