clock命令

clock ----获取时间和操作时间

语法:
clock option ?arg arg ...?

该命令可以用来获取或者操作表示时间的字符串或者数值。option选项决定该命令执行的操作。合法的option如下:

clock clicks ?-milliseconds?
    高解析度计数器，精度为ms，也可以是系统自行确定

clock scan string ?-base clock? ?-gmt boolean?
    解析string字符串并返回秒值。clock值决定于string
    
clock seconds
    以秒数返回当前时间
   
clock format value ?-format str?
    根据str格式化时钟值   
clock format的有效描述符:
%%
    插入 %.

%a
    星期名字的缩写 (Mon, Tue, etc.).

%A
    星期名字的全称 (Monday, Tuesday, etc.).

%b
    月份名字的缩写 (Jan, Feb, etc.).

%B
    月份名字的全称

%c
    特定的时间和日期。 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 specific long date and time, as specified in the Regional Options control panel settings.

%C
    四位年份的头两位 (19 or 20).

%d
    月份内的天数 (01 - 31).

%D
    以 %m/%d/%y 显式的日期

%e
    月份的日期，没有头0

%g
    The ISO8601 year number corresponding to the ISO8601 week (%V), expressed as a two-digit year-of-the-century, with leading zero if necessary.

%G
    The ISO8601 year number corresponding to the ISO8601 week (%V), expressed as a four-digit number.

%h
    缩写的月份名称

%H
    24小时的时间表示 (00 - 23).

%I
    12小时的时间表示 (01 - 12).

%j
    一年中的某一天数 (001 - 366).

%k
    Hour in 24-hour format, without leading zeros (0 - 23).

%l
    Hour in 12-hour format, without leading zeros (1 - 12).

%m
    月份数 (01 - 12).

%M
    分钟数 (00 - 59).

%n
    插入新行

%p
    AM/PM 提示

%r
    Time in a locale-specific "meridian" format. The "meridian" format in the default "C" locale is "%I:%M:%S %p".

%R
    以 %H:%M 显式的时间

%s
    Count of seconds since the epoch, expressed as a decimal integer.

%S
    秒数 (00 - 59).

%t
    插入制表符

%T
    以%H:%M:%S计时

%u
    星期代表的数字 (Monday = 1, Sunday = 7).

%U
    一年的星期数 (00 - 52), Sunday is the first day of the week.

%V
    Week of year according to ISO-8601 rules. Week 1 of a given year is the week containing 4 January.

%w
    星期代表的数字 (Sunday = 0, Saturday = 6).

%W
    一年的星期数 (00 - 52), Monday is the first day of the week.

%x
    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.

%X
    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 specific 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.


举例:
对于clock format value ?-format str?
默认方式以"%a %b %d %H:%M:%S %Z %Y"输出时间

clock format [clock seconds]和clock format [clock seconds] -format "%a %b %d %H:%M:%S %Z %Y"输出效果一样

clock format [clock second] -format "%a %b %d %H:%M:%S %Z %Y"
=> Fri Nov 22 4:09:14 PM PST 2002

clock format [clock seconds]
=> Fri Nov 22 4:09:14 PM PST 2002


对于clock scan string ?-base clock? ?-gmt boolean?

clock scan "10:30:44 PM" -base [clock seconds]
=> 2931690644

clock format [clock scan "10:30:44 PM 1 week"]
=> Fri Nov 29 10:30:44 PM PST 2002
clock format [clock scan "10:30:44 PM -1 week"]
Fri Nov 15 10:30:44 PM PST 2002