date - display or set date and time
The utility displays the date and time read from the kernel clock. When used to set the date and time, both the kernel clock and the hardware clock are updated.
Only the superuser may set the date, and if the system securelevel (see securelevel(7)) is greater than 1, the time may not be changed by more than 1 second.
The options are as follows:
When setting values (rather than adjusting them), seconds are in the range 0-59, minutes are in the range 0-59, hours are in the range 0-23, month days are in the range 1-31, week days are in the range 0-6 (Sun-Sat), months are in the range 1-12 (Jan-Dec) and years are in the range 80-38 or 1980-2038.
If val is numeric, one of either y m w d H M or S must be used to specify which part of the date is to be adjusted.
The week day or month may be specified using a name rather than a number. If a name is used with the plus (or minus) sign, the date will be put forwards (or backwards) to the next (previous) date that matches the given week day or month. This will not adjust the date, if the given week day or month is the same as the current one.
When a date is adjusted to a specific value or in units greater than hours, daylight savings time considerations are ignored. Adjustments in units of hours or less honor daylight saving time. So, assuming the current date is March 26, 0:30 and that the DST adjustment means that the clock goes forward at 01:00 to 02:00, using -v +1H will adjust the date to March 26, 2:30. Likewise, if the date is October 29, 0:30 and the DST adjustment means that the clock goes back at 02:00 to 01:00, using -v +3H will be necessary to reach October 29, 2:30.
When the date is adjusted to a specific value that does not actually exist (for example March 26, 1:30 BST 2000 in the Europe/London timezone), the date will be silently adjusted forwards in units of one hour until it reaches a valid time. When the date is adjusted to a specific value that occurs twice (for example October 29, 1:30 2000), the resulting timezone will be set so that the date matches the earlier of the two times.
Adjusting the date by months is inherently ambiguous because a month is a unit of variable length depending on the current date. This kind of date adjustment is applied in the most intuitive way. First of all, tries to preserve the day of the month. If it is impossible because the target month is shorter than the present one, the last day of the target month will be the result. For example, using -v +1m on May 31 will adjust the date to June 30, while using the same option on January 30 will result in the date adjusted to the last day of February. This approach is also believed to make the most sense for shell scripting. Nevertheless, be aware that going forth and back by the same number of months may take you to a different date.
Refer to the examples below for further details.
An operand with a leading plus (`+' ) sign signals a user-defined format string which specifies the format in which to display the date and time. The format string may contain any of the conversion specifications described in the strftime(3) manual page, as well as any arbitrary text. A newline (`\n' ) character is always output after the characters specified by the format string. The format string for the default display is ``+%+''
If an operand does not have a leading plus sign, it is interpreted as a value for setting the system's notion of the current date and time. The canonical representation for setting the date and time is:
Everything but the minutes is optional.
Time changes for Daylight Saving Time, standard time, leap seconds, and leap years are handled automatically.
"date ""+DATE: %Y-%m-%d%nTIME: %H:%M:%S"""
DATE: 1987-11-21 TIME: 13:36:16
In the Europe/London timezone, the command:
"date -v1m -v+1y"
"Sun Jan 4 04:15:24 GMT 1998"
where it is currently Mon Aug 4 04:15:24 BST 1997
"date -v1d -v3m -v0y -v-1d"
will display the last day of February in the year 2000:
"Tue Feb 29 03:18:00 GMT 2000"
So will do the command:
"date -v30d -v3m -v0y -v-1m"
because there is no such date as the 30th of February.
"date -v1d -v+1m -v-1d -v-fri"
will display the last Friday of the month:
"Fri Aug 29 04:31:11 BST 1997"
where it is currently Mon Aug 4 04:31:11 BST 1997
sets the date to ``June 13, 1985, 4:27 PM ''
may be used on one machine to print out the date suitable for setting on another. Qq ( Li +%m%d%H%M%Y.%S for use on Linux .
sets the time to 2:32 PM without modifying the date.
Finally the command:
"date -j -f ""%a %b %d %T %Z %Y"" ""`date`"" ""+%s"""
can be used to parse the output from and express it in Epoch time.
Закладки на сайте
Проследить за страницей
Created 1996-2021 by Maxim Chirkov
Добавить, Поддержать, Вебмастеру