Module os

Operating System facilities like date, time and program execution.

Functions

clock () Returns an approximation of the amount in seconds of CPU time used by the program.
date (format, time) Returns a string or a table containing date and time, formatted according to the given string `format`.
difftime (t2, t1) Returns the number of seconds from time `t1` to time `t2`.
execute (command) This function is equivalent to the C function `system`.
exit (code) Calls the C function `exit`, with an optional `code`, to terminate the host program.
getenv (varname) Returns the value of the process environment variable `varname`, or nil if the variable is not defined.
remove (filename) Deletes the file or directory with the given name.
rename (oldname, newname) Renames file or directory named `oldname` to `newname`.
setlocale (locale, category) Sets the current locale of the program.
time (table) Returns the current time when called without arguments, or a time representing the date and time specified by the given table.
tmpname () Returns a string with a file name that can be used for a temporary file.


Functions

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

Parameters:

  • format
  • time
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`.

Parameters:

  • t2
  • t1
execute (command)
This function is equivalent to the C 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.

Parameters:

  • command
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.

Parameters:

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

Parameters:

  • varname
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.

Parameters:

  • filename
rename (oldname, newname)
Renames file or directory named `oldname` to `newname`. If this function fails, it returns nil, plus a string describing the error.

Parameters:

  • oldname
  • newname
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. If `locale` is the empty string, the current locale is set to an implementation-defined native locale. If `locale` is the string "`C`", the current locale is set to the standard C locale. When called with nil as the first argument, this function only returns the name of the current locale for the given category.

Parameters:

  • locale
  • category
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`.

Parameters:

  • table
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. On some systems (POSIX), this function also creates a file with that name, to avoid security risks. (Someone else might create the file with wrong permissions in the time between getting the name and creating the file.) You still have to open the file to use it and to remove it (even if you do not use it). When possible, you may prefer to use `io.tmpfile`, which automatically removes the file when the program ends.
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