Octave Time Functions
Timing Utilities
================
Octave's core set of functions for manipulating time values are
patterned after the corresponding functions from the standard C library.
Several of these functions use a data structure for time that includes
the following elements:
`usec'
Microseconds after the second (0-999999).
`sec'
Seconds after the minute (0-61). This number can be 61 to account
for leap seconds.
`min'
Minutes after the hour (0-59).
`hour'
Hours since midnight (0-23).
`mday'
Day of the month (1-31).
`mon'
Months since January (0-11).
`year'
Years since 1900.
`wday'
Days since Sunday (0-6).
`yday'
Days since January 1 (0-365).
`isdst'
Daylight Savings Time flag.
`zone'
Time zone.
In the descriptions of the following functions, this structure is
referred to as a TM_STRUCT.
- Loadable Function: time ()
Return the current time as the number of seconds since the epoch.
The epoch is referenced to 00:00:00 CUT (Coordinated Universal
Time) 1 Jan 1970. For example, on Monday February 17, 1997 at
07:15:06 CUT, the value returned by `time' was 856163706.
- Function File: ctime (T)
Convert a value returned from `time' (or any other nonnegative
integer), to the local time and return a string of the same form as
`asctime'. The function `ctime (time)' is equivalent to `asctime
(localtime (time))'. For example,
ctime (time ())
=> "Mon Feb 17 01:15:06 1997"
- Loadable Function: gmtime (T)
Given a value returned from time (or any nonnegative integer),
return a time structure corresponding to CUT. For example,
gmtime (time ())
=> {
usec = 0
year = 97
mon = 1
mday = 17
sec = 6
zone = CST
min = 15
wday = 1
hour = 7
isdst = 0
yday = 47
}
- Loadable Function: localtime (T)
Given a value returned from time (or any nonnegative integer),
return a time structure corresponding to the local time zone.
localtime (time ())
=> {
usec = 0
year = 97
mon = 1
mday = 17
sec = 6
zone = CST
min = 15
wday = 1
hour = 1
isdst = 0
yday = 47
}
- Loadable Function: mktime (TM_STRUCT)
Convert a time structure corresponding to the local time to the
number of seconds since the epoch. For example,
mktime (localtime (time ())
=> 856163706
- Function File: asctime (TM_STRUCT)
Convert a time structure to a string using the following five-field
format: Thu Mar 28 08:40:14 1996. For example,
asctime (localtime (time ())
=> "Mon Feb 17 01:15:06 1997\n"
This is equivalent to `ctime (time ())'.
- Loadable Function: strftime (TM_STRUCT)
Format a time structure in a flexible way using `%' substitutions
similar to those in `printf'. Except where noted, substituted
fields have a fixed size; numeric fields are padded if necessary.
Padding is with zeros by default; for fields that display a single
number, padding can be changed or inhibited by following the `%'
with one of the modifiers described below. Unknown field
specifiers are copied as normal characters. All other characters
are copied to the output without change. For example,
strftime ("%r (%Z) %A %e %B %Y", localtime (time ())
=> "01:15:06 AM (CST) Monday 17 February 1997"
Octave's `strftime' function supports a superset of the ANSI C
field specifiers.
Literal character fields:
`%'
% character.
`n'
Newline character.
`t'
Tab character.
Numeric modifiers (a nonstandard extension):
`- (dash)'
Do not pad the field.
`_ (underscore)'
Pad the field with spaces.
Time fields:
`%H'
Hour (00-23).
`%I'
Hour (01-12).
`%k'
Hour (0-23).
`%l'
Hour (1-12).
`%M'
Minute (00-59).
`%p'
Locale's AM or PM.
`%r'
Time, 12-hour (hh:mm:ss [AP]M).
`%R'
Time, 24-hour (hh:mm).
`%s'
Time in seconds since 00:00:00, Jan 1, 1970 (a nonstandard
extension).
`%S'
Second (00-61).
`%T'
Time, 24-hour (hh:mm:ss).
`%X'
Locale's time representation (%H:%M:%S).
`%Z'
Time zone (EDT), or nothing if no time zone is determinable.
Date fields:
`%a'
Locale's abbreviated weekday name (Sun-Sat).
`%A'
Locale's full weekday name, variable length (Sunday-Saturday).
`%b'
Locale's abbreviated month name (Jan-Dec).
`%B'
Locale's full month name, variable length (January-December).
`%c'
Locale's date and time (Sat Nov 04 12:02:33 EST 1989).
`%C'
Century (00-99).
`%d'
Day of month (01-31).
`%e'
Day of month ( 1-31).
`%D'
Date (mm/dd/yy).
`%h'
Same as %b.
`%j'
Day of year (001-366).
`%m'
Month (01-12).
`%U'
Week number of year with Sunday as first day of week (00-53).
`%w'
Day of week (0-6).
`%W'
Week number of year with Monday as first day of week (00-53).
`%x'
Locale's date representation (mm/dd/yy).
`%y'
Last two digits of year (00-99).
`%Y'
Year (1970-).
Most of the remaining functions described in this section are not
patterned after the standard C library. Some are available for
compatiblity with MATLAB and others are provided because they are
useful.
- Function File: clock ()
Return a vector containing the current year, month (1-12), day
(1-31), hour (0-23), minute (0-59) and second (0-61). For example,
clock ()
=> [ 1993, 8, 20, 4, 56, 1 ]
The function clock is more accurate on systems that have the
`gettimeofday' function.
- Function File: date ()
Return the date as a character string in the form DD-MMM-YY. For
example,
date ()
=> "20-Aug-93"
- Function File: etime (T1, T2)
Return the difference (in seconds) between two time values
returned from `clock'. For example:
t0 = clock ();
many computations later...
elapsed_time = etime (clock (), t0);
will set the variable `elapsed_time' to the number of seconds since
the variable `t0' was set.
- Function File: [TOTAL, USER, SYSTEM] = cputime ();
Return the CPU time used by your Octave session. The first output
is the total time spent executing your process and is equal to the
sum of second and third outputs, which are the number of CPU
seconds spent executing in user mode and the number of CPU seconds
spent executing in system mode, respectively. If your system does
not have a way to report CPU time usage, `cputime' returns 0 for
each of its output values. Note that because Octave used some CPU
time to start, it is reasonable to check to see if `cputime' works
by checking to see if the total CPU time used is nonzero.
- Function File: is_leap_year (YEAR)
Return 1 if the given year is a leap year and 0 otherwise. If no
arguments are provided, `is_leap_year' will use the current year.
For example,
is_leap_year (2000)
=> 1
- Function File: tic ()
- Function File: toc ()
These functions set and check a wall-clock timer. For example,
tic ();
many computations later...
elapsed_time = toc ();
will set the variable `elapsed_time' to the number of seconds since
the most recent call to the function `tic'.
If you are more interested in the CPU time that your process used,
you should use the `cputime' function instead. The `tic' and
`toc' functions report the actual wall clock time that elapsed
between the calls. This may include time spent processing other
jobs or doing nothing at all. For example,
tic (); sleep (5); toc ()
=> 5
t = cputime (); sleep (5); cputime () - t
=> 0
(This example also illustrates that the CPU timer may have a fairly
coarse resolution.)
- Built-in Function: pause (SECONDS)
Suspend the execution of the program. If invoked without any
arguments, Octave waits until you type a character. With a
numeric argument, it pauses for the given number of seconds. For
example, the following statement prints a message and then waits 5
seconds before clearing the screen.
fprintf (stderr, "wait please...
");
pause (5);
clc;
- Built-in Function: sleep (SECONDS)
Suspend the execution of the program for the given number of
seconds.
- Built-in Function: usleep (MICROSECONDS)
Suspend the execution of the program for the given number of
microseconds. On systems where it is not possible to sleep for
periods of time less than one second, `usleep' will pause the
execution for `round (MICROSECONDS / 1e6)' seconds.