Linux 时间&时区

shell没有专门的时间转换函数,更没有oop之类的类方法,不过操作时间还是很简单的

date:
date 直接后跟格式化字符串默认显示当前时区的当前时间

%a abbreviated weekday 简写的weekday
%A full weekday name 全写weekday
%b abbreviated month name 简写month
%B full month name 全写month name
%c locale's DATE and TIME
%F full date, same as %Y-%m-%d
%j day of year,今天是今年的第几天
%s seconds since 1970-01-01 00:00:00 UTC 注意时区
%S 当前秒数(00..60)
%T full time, same as%H:%M:%S
%z +hhmm numeric time zone (e.g. -0400)
%Z alphebatic time zone abbreviation (e.g. EDT)

Options:

date 后跟+%FORMAT_STRING来格式化时间
```
date '+The Current Datetime: %c'
```

--date=STRING Display time described by string not now
进行时间计算

date -d '1 second' +%c  # 1 second later
date -d '-1 second' +%c  # 1 second ago
date -d '1 minute' +%c  # 1 minute later
date -d '-1 minute' +%c  # 1 minute ago
date -d '1 hour' +%c  # 1 hour later
date -d '-1 hour' +%c  # 1 hour ago
date -d '1 day' +%c  # 1 day later
date -d '-1 day' +%c  # 1 day ago
date -d '1 week' +%c  # 1 week later
date -d '-1 week' +%c  # 1 week ago
date -d '1 month' +%c  # 1 month later
date -d '-1 month' +%c  # 1 month ago
date -d '1 year' +%c  # 1 year later
date -d '-1 year' +%c  # 1 year ago

-d "@timestamp" 转换时间戳

@后跟时间戳即可

--reference 显示文件最后修改时间
```
date --reference file
```
--utc 显示UTC时间

--set 设置时间

date --set 1:1:1  # 设置时间,日期保持不变

date -s '1999:1:1 1:1'  # 同时修改日期和时间

计算时间脚本

s=`date +'%H:%M:%S'`
echo -e Incept Time: "\t$s"
sleep 2
e=`date +'%H:%M:%S'`
echo -e Closure Time: "\t$e"

s=$(date --date=$s +%s)
e=$(date --date=$e +%s)

echo -e Elapsed: "\t$[e-s]" seconds

s=`date +%s`
nmap -v -A -sV -F scanme.nmap.org
e=`date +%s`
difference=$((e-s))
echo -e Elapsed: "\t$difference"

Linux设定时区:

tzselect命令
覆盖/etc/localtime软连接
```
ln -svfn /usr/share/zoneinfo/America/New_York /etc/localtime
```
一定要连接正确,如果/etc/localtime没有连接到正确时区,会显示UTC时间
设置系统变量TZ,该变量默认没有设置,此变量优先级最高
```
echo 'export TZ="Asia/Shanghai"' >> ~/.bashrc
source ~/.bashrc
```
通过timedatectl
systemd默认有一个systemd类型的static服务
```
timedatectl status
```
```
timedatectl set-timezone 'America/New_York'
```
优先级依然低于TZ变量