Perl 简明教程

Perl - Date and Time

本章将向您介绍如何在 Perl 中处理和操作日期和时间。

This chapter will give you the basic understanding on how to process and manipulate dates and times in Perl.

Current Date and Time

让我们从 localtime() 函数开始，如果不传递参数，该函数将返回当前日期和时间的值。下面是 localtime 函数在列表上下文中使用时返回的 9 个元素的列表 −

Let’s start with localtime() function, which returns values for the current date and time if given no arguments. Following is the 9-element list returned by the localtime function while using in list context −

sec,     # seconds of minutes from 0 to 61
min,     # minutes of hour from 0 to 59
hour,    # hours of day from 0 to 24
mday,    # day of month from 1 to 31
mon,     # month of year from 0 to 11
year,    # year since 1900
wday,    # days since sunday
yday,    # days since January 1st
isdst    # hours of daylight savings time

尝试以下示例来打印 localtime() 函数返回的不同元素 −

Try the following example to print different elements returned by localtime() function −

#!/usr/local/bin/perl

@months = qw( Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec );
@days = qw(Sun Mon Tue Wed Thu Fri Sat Sun);

($sec,$min,$hour,$mday,$mon,$year,$wday,$yday,$isdst) = localtime();
print "$mday $months[$mon] $days[$wday]\n";

执行上述代码后，将生成以下结果 −

When the above code is executed, it produces the following result −

16 Feb Sat

如果你将在标量上下文中使用 localtime() 函数，它将从系统中设置的当前时区返回日期和时间。尝试以下示例以完整格式打印当前日期和时间 −

If you will use localtime() function in scalar context, then it will return date and time from the current time zone set in the system. Try the following example to print current date and time in full format −

#!/usr/local/bin/perl

$datestring = localtime();
print "Local date and time $datestring\n";

执行上述代码后，将生成以下结果 −

When the above code is executed, it produces the following result −

Local date and time Sat Feb 16 06:50:45 2013

GMT Time

函数 gmtime() 的工作方式与 localtime() 函数类似，但返回的值是针对标准格林尼治时区的本地化。在列表上下文中调用时，$isdst 是 gmtime 返回的最后一个值，它始终为 0。格林尼治标准时间没有夏令时。

The function gmtime() works just like localtime() function but the returned values are localized for the standard Greenwich time zone. When called in list context, $isdst, the last value returned by gmtime, is always 0. There is no Daylight Saving Time in GMT.

您应该注意到 localtime() 会返回运行该脚本的机器上的当前本地时间，而 gmtime() 会返回标准世界时间（世界协调时间，即 GMT 或 UTC）。

You should make a note on the fact that localtime() will return the current local time on the machine that runs the script and gmtime() will return the universal Greenwich Mean Time, or GMT (or UTC).

尝试以下示例来打印当前日期和时间（但使用 GMT 的时间标度）：

Try the following example to print the current date and time but on GMT scale −

#!/usr/local/bin/perl

$datestring = gmtime();
print "GMT date and time $datestring\n";

执行上述代码后，将生成以下结果 −

When the above code is executed, it produces the following result −

GMT date and time Sat Feb 16 13:50:45 2013

Format Date and Time

您可以使用 localtime() 函数获取一个包含 9 个元素的列表，然后可以使用 printf() 函数根据您的需求对日期和时间进行如下格式化：

You can use localtime() function to get a list of 9-elements and later you can use the printf() function to format date and time based on your requirements as follows −

#!/usr/local/bin/perl

($sec,$min,$hour,$mday,$mon,$year,$wday,$yday,$isdst) = localtime();

printf("Time Format - HH:MM:SS\n");
printf("%02d:%02d:%02d", $hour, $min, $sec);

执行上述代码后，将生成以下结果 −

When the above code is executed, it produces the following result −

Time Format - HH:MM:SS
06:58:52

Epoch time

您可以使用 time() 函数获取纪元时间，即从 1970 年 1 月 1 日（Unix 纪元时间）开始到现在经过的秒数。

You can use the time() function to get epoch time, i.e., the numbers of seconds that have elapsed since a given date, in Unix is January 1, 1970.

#!/usr/local/bin/perl

$epoc = time();

print "Number of seconds since Jan 1, 1970 - $epoc\n";

执行上述代码后，将生成以下结果 −

When the above code is executed, it produces the following result −

Number of seconds since Jan 1, 1970 - 1361022130

您可以将给定的秒数转换为日期和时间字符串，如下所示：

You can convert a given number of seconds into date and time string as follows −

#!/usr/local/bin/perl

$datestring = localtime();
print "Current date and time $datestring\n";

$epoc = time();
$epoc = $epoc - 24 * 60 * 60;   # one day before of current date.

$datestring = localtime($epoc);
print "Yesterday's date and time $datestring\n";

执行上述代码后，将生成以下结果 −

When the above code is executed, it produces the following result −

Current date and time Tue Jun  5 05:54:43 2018
Yesterday's date and time Mon Jun  4 05:54:43 2018

POSIX Function strftime()

您可以使用 POSIX 函数 strftime() 在下表的帮助下对日期和时间进行格式化。请注意，标记有星号 (*) 的说明符是与区域设置相关的。

You can use the POSIX function strftime() to format date and time with the help of the following table. Please note that the specifiers marked with an asterisk (*) are locale-dependent.

Specifier

Replaced by

Example

%a

Abbreviated weekday name *

Thu

%A

Full weekday name *

Thursday

%b

Abbreviated month name *

Aug

%B

Full month name *

August

%c

Date and time representation *

Thu Aug 23 14:55:02 2001

%C

Year divided by 100 and truncated to integer (00-99)

20

%d

Day of the month, zero-padded (01-31)

23

%D

Short MM/DD/YY date, equivalent to %m/%d/%y

08/23/01

%e

Day of the month, space-padded ( 1-31)

23

%F

Short YYYY-MM-DD date, equivalent to %Y-%m-%d

2001-08-23

%g

Week-based year, last two digits (00-99)

01

%G

Week-based year

2001

%h

Abbreviated month name * (same as %b)

Aug

%H

Hour in 24h format (00-23)

14

%I

Hour in 12h format (01-12)

02

%j

Day of the year (001-366)

235

%m

Month as a decimal number (01-12)

08

%M

Minute (00-59)

55

%n

New-line character ('\n')

%p

AM or PM designation

PM

%r

12-hour clock time *

02:55:02 pm

%R

24-hour HH:MM time, equivalent to %H:%M

14:55

%S

Second (00-61)

02

%t

Horizontal-tab character ('\t')

%T

ISO 8601 time format (HH:MM:SS), equivalent to %H:%M:%S

14:55

%u

ISO 8601 weekday as number with Monday as 1 (1-7)

4

%U

Week number with the first Sunday as the first day of week one (00-53)

33

%V

ISO 8601 week number (00-53)

34

%w

Weekday as a decimal number with Sunday as 0 (0-6)

4

%W

Week number with the first Monday as the first day of week one (00-53)

34

%x

Date representation *

08/23/01

%X

Time representation *

14:55:02

%y

Year, last two digits (00-99)

01

%Y

Year

2001

%z

ISO 8601 offset from UTC in timezone (1 minute = 1, 1 hour = 100) If timezone cannot be termined, no characters

+100

%Z

Timezone name or abbreviation * If timezone cannot be termined, no characters

CDT

%%

A % sign

%

让我们看看以下示例以了解用法 -

Let’s check the following example to understand the usage −

#!/usr/local/bin/perl
use POSIX qw(strftime);

$datestring = strftime "%a %b %e %H:%M:%S %Y", localtime;
printf("date and time - $datestring\n");

# or for GMT formatted appropriately for your locale:
$datestring = strftime "%a %b %e %H:%M:%S %Y", gmtime;
printf("date and time - $datestring\n");

执行上述代码后，将生成以下结果 −

When the above code is executed, it produces the following result −

date and time - Sat Feb 16 07:10:23 2013
date and time - Sat Feb 16 14:10:23 2013