How many formats do you know about Shell date under Linux?

Regardless of the language, date/time is a very important value. For example, when we save logs, we often use a certain prefix plus the current time, so that the log file name can be unique.

In the Shell environment, our command to get the time is date, but the time and date format and content of the date may not be what we want, so we may need to format it for output.

The commonly used time domains are as follows:

% Y year (for example: 1970, 2018, etc.)

% m month (01..12)

% d Day of the month (01..31)

% H hours (00..23)

% M minutes (00..59)

% S seconds (00..59)

Use the date command without parameters to get the current time and date. The time obtained in this way is generally in the CST standard format.

[alvin@VM_0_16_centos ~]$ date
Sat Nov  3 22:01:57 CST 2018

To get a specific format, the command is: date +'format'. Note that this is case sensitive.

[alvin@VM_0_16_centos ~]$ date +'%Y-%m-%d'
2018-11-03
[alvin@VM_0_16_centos ~]$ date +'%Y/%m/%d %H:%M:%S'
2018/11/03 22:08:14

Get yesterday's date. The -d option can be added to the above command.

[alvin@VM_0_16_centos ~]$ date -d 'yesterday' +'%Y/%m/%d %H:%M:%S'
2018/11/02 22:24:31

或者

[alvin@VM_0_16_centos ~]$ date -d 'today -1 day' +'%Y-%m-%d'
2018-11-04

Get the hour before the current time

[alvin@VM_0_16_centos ~]$ date -d 'today -1 hour' +'%Y%m%d%H'
2018110414

或者

[alvin@VM_0_16_centos ~]$ date +'%Y-%m-%d %H:%M:%S' -d '-1 hours'
2018-11-04 14:43:38

Get the day before the specified date. This is actually seeking relative time. For example, the following is the date before the National Day:

[alvin@VM_0_16_centos ~]$ date -d '20181001 -1 day' +'%Y%m%d'
20180930

Convert date to timestamp

[alvin@VM_0_16_centos ~]$ date -d "Nov  4 15:49:41 CST 2018" +%s
1541317781

Convert timestamp back to date

[alvin@VM_0_16_centos ~]$ date -d @1541317781
Sun Nov  4 15:49:41 CST 2018

Convert the timestamp to a date and display it in a specific format

[alvin@VM_0_16_centos ~]$ date -d @1541317781 +'%Y%m%d %H:%M:%S'
20181104 15:49:41

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