本文出自作者学习鸟哥linux私房菜的学习笔记
如有雷同绝不是巧合
一 man
linux里边有句俗语叫做有问题找男人，这个男人就是man （manual）
man 命令名称就能得到详细的命令的相关解释
（1）eg：man date
DATE(1) User Commands DATE(1)
#请注意上边这个括号内的数字
NAME <==这个命令的完整全名，如下所示为date且说明简单用途为设置与显示日期/时间
date - print or set the system date and time
SYNOPSIS <==这个命令的基本语法如下所示
date [OPTION]... [+FORMAT]
date [-u|--utc|--universal] [MMDDhhmm[[CC]YY][.ss]]
DESCRIPTION <==详细说明刚才语法谈到的参数的用法
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
#………………中间省略若干字
#下面就是格式化输出的详细数据
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 (e.g., Sun)
%A locale’s full weekday name (e.g., Sunday)
%b locale’s abbreviated month name (e.g., Jan)
%B locale’s full month name (e.g., January)
%c locale’s date and time (e.g., Thu Mar 3 23:05:25 2005)
%C century; like %Y, except omit last two digits (e.g., 21)
%d day of month (e.g, 01)
%D date; same as %m/%d/%y
%e day of month, space padded; same as %_d
%F full date; same as %Y-%m-%d
%g last two digits of year of ISO week number (see %G)
%G year of ISO week number (see %V); normally useful only with %V
%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 equivalent of either AM or PM; blank if not known
%P like %p, but lower case
%r locale’s 12-hour clock time (e.g., 11:11:04 PM)
%R 24-hour hour and minute; same as %H:%M
%s seconds since 1970-01-01 00:00:00 UTC
%S second (00..60)
%t a tab
%T time; same as %H:%M:%S
%u day of week (1..7); 1 is Monday
%U week number of year, with Sunday as first day of week (00..53)
%V ISO week number, with Monday as first day of week (01..53)
%w day of week (0..6); 0 is Sunday
%W week number of year, with Monday as first day of week (00..53)
%x locale’s date representation (e.g., 12/31/99)
%X locale’s time representation (e.g., 23:13:48)
%y last two digits of year (00..99)
%Y year
%z +hhmm numeric timezone (e.g., -0400)
%:z +hh:mm numeric timezone (e.g., -04:00)
%::z +hh:mm:ss numeric time zone (e.g., -04:00:00)
%:::z numeric time zone with : to necessary precision (e.g., -04,
+05:30)
%Z alphabetic time zone abbreviation (e.g., EDT)
ENVIRONMENT <==与这个命令相关的环境参数有如下说明
TZ Specifies the timezone, unless overridden by command line param-
eters. If neither is specified, the setting from /etc/localtime
is used.
AUTHOR <==这个命令的作者
Written by David MacKenzie.
REPORTING BUGS <==有问题请致信下面的邮箱
Report bugs to <bug-coreutils@gnu.org>.
COPYRIGHT <==受到著作权法的保护，用的就是GPL了
Copyright © 2006 Free Software Foundation, Inc.
This is free software. You may redistribute copies of it under the
terms of the GNU General Public License
<http://www.gnu.org/licenses/gpl.html>. There is NO WARRANTY, to the
extent permitted by law.
SEE ALSO <==这个重要，你还可以从哪里查到与date相关的说明文件之意
The full documentation for date is maintained as a Texinfo manual. If
the info and date programs are properly installed at your site, the
command
info date
should give you access to the complete manual.
date 5.97 March 2011 DATE(1)
