clock(n) Tcl Built-In Commands clock(n)______________________________________________________________________________NAMEclock - Obtain and manipulate time
SYNOPSISclock option ?arg arg ...?
This command performs one of several operations that may obtain or
manipulate strings or values that represent some notion of time. The
option argument determines what action is carried out by the command.
The legal options (which may be abbreviated) are:
clock clicks ?-milliseconds? │
Return a high-resolution time value as a system-dependent inte‐ │
ger value. The unit of the value is system-dependent but should │
be the highest resolution clock available on the system such as │
a CPU cycle counter. If -milliseconds is specified, then the │
value is guaranteed to be of millisecond granularity. This │
value should only be used for the relative measurement of │
clock format clockValue ?-format string? ?-gmt boolean?
Converts an integer time value, typically returned by clock sec‐
onds, clock scan, or the atime, mtime, or ctime options of the
file command, to human-readable form. If the -format argument
is present the next argument is a string that describes how the
date and time are to be formatted. Field descriptors consist of
a % followed by a field descriptor character. All other charac‐
ters are copied into the result. Valid field descriptors are:
%% Insert a %.
%a Abbreviated weekday name (Mon, Tue, etc.).
%A Full weekday name (Monday, Tuesday, etc.).
%b Abbreviated month name (Jan, Feb, etc.).
%B Full month name. │
Locale specific date and time. The format for date and │
time in the default "C" locale on Unix/Mac is "%a %b %d │
%H:%M:%S %Y". On Windows, this value is the locale spe‐ │
cific long date and time, as specified in the Regional │
Options control panel settings. │
First two digits of the four-digit year (19 or 20).
%d Day of month (01 - 31). │
Date as %m/%d/%y. │
Day of month (1 - 31), no leading zeros. │
Abbreviated month name.
%H Hour in 24-hour format (00 - 23). │
Hour in 12-hour format (01 - 12).
%j Day of year (001 - 366). │
Hour in 24-hour format, without leading zeros (0 - 23). │
Hour in 12-hour format, without leading zeros (1 - 12).
%m Month number (01 - 12).
%M Minute (00 - 59). │
Insert a newline.
%p AM/PM indicator. │
Time in a locale-specific "meridian" format. The "merid‐ │
ian" format in the default "C" locale is "%I:%M:%S %p". │
Time as %H:%M. │
Count of seconds since the epoch, expressed as a decimal │
%S Seconds (00 - 59). │
Insert a tab. │
Time as %H:%M:%S. │
Weekday number (Monday = 1, Sunday = 7).
%U Week of year (00 - 52), Sunday is the first day of the
Week of year according to ISO-8601 rules. Week 1 of a │
given year is the week containing 4 January. │
Weekday number (Sunday = 0, Saturday = 6).
%W Week of year (00 - 52), Monday is the first day of the
Locale specific date format. The format for a date in │
the default "C" locale for Unix/Mac is "%m/%d/%y". On │
Windows, this value is the locale specific short date │
format, as specified in the Regional Options control │
panel settings. │
Locale specific 24-hour time format. The format for a │
24-hour time in the default "C" locale for Unix/Mac is │
"%H:%M:%S". On Windows, this value is the locale spe‐ │
cific time format, as specified in the Regional Options │
control panel settings.
%y Year without century (00 - 99).
%Y Year with century (e.g. 1990)
%Z Time zone name.
If the -format argument is not specified, the format string "%a │
%b %d %H:%M:%S %Z %Y" is used. If the -gmt argument is present
the next argument must be a boolean which if true specifies that
the time will be formatted as Greenwich Mean Time. If false then
the local timezone will be used as defined by the operating
clock scan dateString ?-base clockVal? ?-gmt boolean?
Convert dateString to an integer clock value (see clock sec‐
onds). This command can parse and convert virtually any stan‐
dard date and/or time string, which can include standard time
zone mnemonics. If only a time is specified, the current date
is assumed. If the string does not contain a time zone
mnemonic, the local time zone is assumed, unless the -gmt argu‐
ment is true, in which case the clock value is calculated assum‐
ing that the specified time is relative to Greenwich Mean Time.
-gmt, if specified, affects only the computed time value; it
does not impact the interpretation of -base.
If the -base flag is specified, the next argument should contain
an integer clock value. Only the date in this value is used,
not the time. This is useful for determining the time on a spe‐
cific day or doing other date-relative conversions.
The dateString consists of zero or more specifications of the
time A time of day, which is of the form: hh?:mm?:ss??
?meridian? ?zone? or hhmm ?meridian? ?zone?. If no
meridian is specified, hh is interpreted on a 24-hour
date A specific month and day with optional year. The accept‐
able formats are mm/dd?/yy?, monthname dd ?, yy?, dd mon‐
thname ?yy?, day, dd monthname yy, ?CC?yymmdd, ?CC?yy-mm-
dd, dd-monthname-?CC?yy. The default year is the current
year. If the year is less than 100, we treat the years │
00-68 as 2000-2068 and the years 69-99 as 1969-1999. Not │
all platforms can represent the years 38-70, so an error │
may result if these years are used.
ISO 8601 point-in-time
An ISO 8601 point-in-time specification, such as CCyymmd‐
dThhmmss, where T is the literal T, CCyymmdd hhmmss, or
A specification relative to the current time. The format
is number unit acceptable units are year, fortnight,
month, week, day, hour, minute (or min), and second (or
sec). The unit can be specified as a singular or plural,
as in 3 weeks. These modifiers may also be specified:
tomorrow, yesterday, today, now, last, this, next, ago.
The actual date is calculated according to the following steps.
First, any absolute date and/or time is processed and converted.
Using that time as the base, day-of-week specifications are
added. Next, relative specifications are used. If a date or
day is specified, and no absolute or relative time is given,
midnight is used. Finally, a correction is applied so that the
correct hour of the day is produced after allowing for daylight
savings time differences and the correct date is given when
going from the end of a long month to a short month.
Daylight savings time correction is applied only when the rela‐
tive time is specified in units of days or more, ie, days,
weeks, fortnights, months or years. This means that when cross‐
ing the daylight savings time boundary, different results will
be given for clock scan "1 day" and clock scan "24 hours":
% clock scan "1 day" -base [clock scan 1999-10-31]
% clock scan "24 hours" -base [clock scan 1999-10-31]
Return the current date and time as a system-dependent integer
value. The unit of the value is seconds, allowing it to be used
for relative time calculations. The value is usually defined as
total elapsed time from an ``epoch''. You shouldn't assume the
value of the epoch.
SEE ALSOdate(1), time(n)KEYWORDS
clock, date, time
Tcl 8.4 clock(n)