linux中使用date和clock命令查到的时间为什么不一致

                                  linux中使用date和clock命令查到的时间为什么不一致

date查询和修改的是系统时间，clock查询和修改的是CPU硬件时间，两个时间可以单独修改和查询。可以使用clock –w命令将CPU时间同步到系统时间。

附1：date帮助

[root@iVS-VM8000-Server ~]# date --help

Usage: date [OPTION]... [+FORMAT]

  or:  date [-u|--utc|--universal] [MMDDhhmm[[CC]YY][.ss]]

Display the current time in the given FORMAT, or set the system date.

  -d, --date=STRING         display time described by STRING, not `now'

  -f, --file=DATEFILE       like --date once for each line of DATEFILE

  -ITIMESPEC, --iso-8601[=TIMESPEC]  output date/time in ISO 8601 format.

                            TIMESPEC=`date' for date only,

                            `hours', `minutes', or `seconds' for date and

                            time to the indicated precision.

                            --iso-8601 without TIMESPEC defaults to `date'.

  -r, --reference=FILE      display the last modification time of FILE

  -R, --rfc-2822            output RFC-2822 compliant date string

  -s, --set=STRING          set time described by STRING

  -u, --utc, --universal    print or set Coordinated Universal Time

      --help     display this help and exit

      --version  output version information and exit

FORMAT controls the output.  The only valid option for the second form

specifies Coordinated Universal Time.  Interpreted sequences are:

  %%   a literal %

  %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 (year divided by 100 and truncated to an integer) [00-99]

  %d   day of month (01..31)

  %D   date (mm/dd/yy)

  %e   day of month, blank padded ( 1..31)

  %F   same as %Y-%m-%d

  %g   the 2-digit year corresponding to the %V week number

  %G   the 4-digit year corresponding to the %V week number

  %h   same as %b

  %H   hour (00..23)

  %I   hour (01..12)

  %j   day of year (001..366)

  %k   hour ( 0..23)

  %l   hour ( 1..12)

  %m   month (01..12)

  %M   minute (00..59)

  %n   a newline

  %N   nanoseconds (000000000..999999999)

  %p   locale's upper case AM or PM indicator (blank in many locales)

  %P   locale's lower case am or pm indicator (blank in many locales)

  %r   time, 12-hour (hh:mm:ss [AP]M)

  %R   time, 24-hour (hh:mm)

  %s   seconds since `00:00:00 1970-01-01 UTC' (a GNU extension)

  %S   second (00..60); the 60 is necessary to accommodate a leap second

  %t   a horizontal tab

  %T   time, 24-hour (hh:mm:ss)

  %u   day of week (1..7);  1 represents Monday

  %U   week number of year with Sunday as first day of week (00..53)

  %V   week number of year with Monday as first day of week (01..53)

  %w   day of week (0..6);  0 represents Sunday

  %W   week number of year with Monday as first day of week (00..53)

  %x   locale's date representation (mm/dd/yy)

  %X   locale's time representation (%H:%M:%S)

  %y   last two digits of year (00..99)

  %Y   year (1970...)

  %z   RFC-2822 style numeric timezone (-0500) (a nonstandard extension)

  %Z   time zone (e.g., EDT), or nothing if no time zone is determinable

By default, date pads numeric fields with zeroes.  GNU date recognizes

the following modifiers between `%' and a numeric directive.

  `-' (hyphen) do not pad the field

  `_' (underscore) pad the field with spaces

Report bugs to <bug-coreutils@***.***>.

[root@iVS-VM8000-Server ~]#

附2：clock帮助

[root@iVS-VM8000-Server ~]# clock --help

hwclock - query and set the hardware clock (RTC)

Usage: hwclock [function] [options...]

Functions:

  --help        show this help

  --show        read hardware clock and print result

  --set         set the rtc to the time given with --date

  --hctosys     set the system time from the hardware clock

  --systohc     set the hardware clock to the current system time

  --adjust      adjust the rtc to account for systematic drift since

                the clock was last set or adjusted

  --getepoch    print out the kernel's hardware clock epoch value

  --setepoch    set the kernel's hardware clock epoch value to the

                value given with --epoch

  --version     print out the version of hwclock to stdout

Options:

  --utc         the hardware clock is kept in coordinated universal time

  --localtime   the hardware clock is kept in local time

  --directisa   access the ISA bus directly instead of /dev/rtc

  --badyear     ignore rtc's year because the bios is broken

  --date        specifies the time to which to set the hardware clock

  --epoch=year  specifies the year which is the beginning of the

                hardware clock's epoch value

  --noadjfile   do not access /etc/adjtime. Requires the use of

                either --utc or --localtime

[root@iVS-VM8000-Server ~]#