luaposix 38

• Index

Contents

• Functions
• Tables
• Constants

Modules

• posix
• posix.ctype
• posix.dirent
• posix.errno
• posix.fcntl
• posix.fnmatch
• posix.glob
• posix.grp
• posix.libgen
• posix.poll
• posix.pwd
• posix.sched
• posix.signal
• posix.stdio
• posix.stdlib
• posix.sys.msg
• posix.sys.resource
• posix.sys.socket
• posix.sys.stat
• posix.sys.statvfs
• posix.sys.time
• posix.sys.times
• posix.sys.utsname
• posix.sys.wait
• posix.syslog
• posix.termio
• posix.time
• posix.unistd
• posix.utime

Examples

• abstract-ns-client.lua
• abstract-ns-server.lua
• dir.lua
• dup2.lua
• fork.lua
• fork2.lua
• getopt.lua
• glob.lua
• limit.lua
• lock.lua
• netlink-uevent.lua
• packet-socket.lua
• ping.lua
• poll.lua
• rt_sched.lua
• signal.lua
• socket.lua
• termios.lua
• tree.lua

Module posix.time

Time and Clock Functions.

Functions

clock_getres (clk)	Find the precision of a clock.
clock_gettime (clk)	Read a clock.
gmtime (t)	Convert epoch time value to a broken-down UTC time.
localtime (t)	Convert epoch time value to a broken-down local time.
mktime (broken)	Convert a broken-down localtime table into an epoch time.
nanosleep (requested)	Sleep with nanosecond precision.
strftime (format, tm)	Return a time string according to format.
strptime (s, format)	Parse a date string.
time ()	Get current time.
tzset ()	Apply the TZ environment variable to the timezone information used by functions such as localtime, mktime and strftime.

Tables

PosixTimespec	Timespec record.
PosixTm	Datetime record.

Constants

posix.time

Standard constants.

Functions

clock_getres (clk)

Find the precision of a clock.

Parameters:

• clk int name of clock, one of CLOCK_REALTIME, CLOCK_PROCESS_CPUTIME_ID, CLOCK_MONOTONIC or CLOCK_THREAD_CPUTIME_ID

Returns:

PosixTimespec resolution of clk, if successful

Or

1. nil
2. string error message
3. int errnum

See also:

clock_getres(3)

clock_gettime (clk)

Read a clock.

Parameters:

• clk int name of clock, one of CLOCK_REALTIME, CLOCK_PROCESS_CPUTIME_ID, CLOCK_MONOTONIC or CLOCK_THREAD_CPUTIME_ID

Returns:

PosixTimespec current value of clk, if successful

Or

1. nil
2. string error message
3. int errnum

See also:

clock_gettime(3)

gmtime (t)

Convert epoch time value to a broken-down UTC time.

Parameters:

• t int seconds since epoch

Returns:

PosixTm broken-down time, if successful

Or

1. nil
2. string error message
3. int errnum

See also:

gmtime(3)

localtime (t)

Convert epoch time value to a broken-down local time.

Parameters:

• t int seconds since epoch

Returns:

PosixTm broken-down time, if successful

Or

1. nil
2. string error message
3. int errnum

See also:

• localtime(3)
• mktime

mktime (broken)

Convert a broken-down localtime table into an epoch time.

Parameters:

• broken PosixTm -down localtime

Returns:

int seconds since epoch

See also:

• mktime(3)
• localtime

nanosleep (requested)

Sleep with nanosecond precision.

Parameters:

• requested PosixTimespec sleep time

Returns:

int 0 if requested time has elapsed, if successful

Or

1. nil
2. string error message
3. int errnum
4. PosixTimespec unslept time remaining, if interrupted

See also:

• nanosleep(2)
• posix.unistd.sleep

strftime (format, tm)

Return a time string according to format. Note that if your host POSIX library provides a strftime that assumes the local timezone, %z will always print the local UTC offset, regardless of the tm_gmoffset field value passed in.

Parameters:

• format string specifier with % place-holders
• tm PosixTm broken-down local time

Returns:

string format with place-holders plugged with tm values

See also:

strftime(3)

strptime (s, format)

Parse a date string.

Parameters:

• s string
• format string same as for strftime

Returns:

1. PosixTm broken-down local time
2. int next index of first character not parsed as part of the date, if successful

Or

nil

See also:

strptime(3)

Usage:

posix.strptime('20','%d').monthday == 20

time ()

Get current time.

Returns:

int time in seconds since epoch, if successful

Or

1. nil
2. string error message
3. int errnum

See also:

time(2)

tzset ()

Apply the TZ environment variable to the timezone information used by functions such as localtime, mktime and strftime.

Some C libraries, such as the GNU one, do not notice a change of TZ made with posix.stdlib.setenv until tzset is called.

See also:

tzset(3)

Usage:

local stdlib = require "posix.stdlib"
local time = require "posix.time"
stdlib.setenv("TZ", "UTC0")
time.tzset()

Tables

PosixTimespec

Timespec record.

Fields:

• tv_sec int seconds
• tv_nsec int nanoseconds

See also:

posix.sys.time.PosixTimeval

PosixTm

Datetime record.

Fields:

• tm_sec int second [0,60]
• tm_min int minute [0,59]
• tm_hour int hour [0,23]
• tm_mday int day of month [1, 31]
• tm_mon int month of year [0,11]
• tm_year int years since 1900
• tm_wday int day of week [0=Sunday,6]
• tm_yday int day of year [0,365[
• tm_isdst int 0 if daylight savings time is not in effect

Constants

posix.time

Standard constants. Any constants not available in the underlying system will be nil valued.

Fields:

• CLOCK_MONOTONIC int the identifier for the system-wide monotonic clock
• CLOCK_PROCESS_CPUTIME_ID int the identifier for the current process CPU-time clock
• CLOCK_REALTIME int the identifier for the system-wide realtime clock
• CLOCK_THREAD_CPUTIME_ID int the identifier for the current thread CPU-time clock

Usage:

-- Print posix.time constants supported on this host.
for name, value in pairs (require "posix.time") do
  if type (value) == "number" then
    print (name, value)
   end
end