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In daily development, I have been engaged in back-end server development for a long time, and I can't avoid dealing with time frequently, for example:

Player's first login time, player's last login time, opening time and ending time of the activity.

The time in the program is represented by a number, which we call a Timestamp.

More often, we use an integer number to represent this timestamp.

Each different integer number has a different meaning, and they all represent a unique time, such as:

0: represents New year's Day 1970 (1970 0.1.1 00:00:00 UTC) 60: represents 1970 New year's Day just after one minute (1970 0.1.1 00:00:60 UTC) 3600: represents 1970 New Year's Day Day passed an hour (1970 0.1.1 01:00:00 UTC) 43200: represents 1970 New Year's Day Day lunchtime (1970 0.1.1 12:00:00 UTC) 86400: represents New Year's Day 1970 The festival is over (1970.1.2 00:00:00 UTC)

Combined with the above example, the definition of a Timestamp is clear. A timestamp is a number that represents the number of seconds that have elapsed since New year's Day in 1970 (1970.1.1 00:00:00).

To clarify this concept, if we see another number and know that it represents a timestamp, we should be eager to convert it to the time it represents.

Chinese dialect

In fact, I just wanted to record the guidelines for using date command-line tools on Linux/Unix, only to recall a brief concept of timestamps.

The reason for this is that for a long time, I got a timestamp and wanted to see which day, year and even minute and second the timestamp was (usually when something went wrong with the program that needed to locate the time-related BUG). I will habitually open a search engine and enter the keyword timestamp to search, and then skillfully click on the first Unix timestamp conversion tool of the search results, until one day I feel that I need to correct this bad habit. I began to try to use date, a command line tool standard in the Linux/Unix system, to complete this daily operation. Haha, I can only be ashamed that I didn't put this useful website in the top column of the browser!

Topic timestamp-> date

As usual, I found a suspicious timestamp in the process of debugging, its value is 1506787200, I need to know which specific date this timestamp corresponds to, so I skillfully opened a search engine to enter the timestamp.

In fact, this time I opened the Mac system terminal (Terminal) and entered the following command:

Date-r 1506787200

This command also gave me accurate feedback output as quickly as possible:

From this moment on, I felt that I had finally got rid of my bad habit, so I felt it necessary to do it a few more times to achieve the purpose of reinforcement, so I skillfully entered the following commands in turn:

Date-r 0date-r 60date-r 3600date-r 43200date-r 86400

These commands eagerly gave me accurate feedback output as quickly as possible:

From this moment on, I felt that I had mastered the meaning of date-r, and just as I was ecstatic, my side light suddenly scanned the output of the command date-r 0: 08:00:00 CST on Thursday, January 1, 1970, why 8 am, and the zero I mentioned earlier means 00:00:00 on January 1, 1970.

In fact, this is a misunderstanding. Timestamp: 0 does represent 00:00:00 on January 1, 1970, but it represents the zero time zone (UTC+0) at 00:00:00 on January 1, 1970. fortunately, I have also studied geography, knowing that our great motherland has a vast territory, vast territory and abundant resources, and that there are five time zones across the light time zone, and the time in the time zone of the capital Beijing (UTC+8) is uniformly used throughout the country.

Because the time zone set by my computer system is East Zone 8, this date command, by default, also shows the converted local time according to the time zone of the system. So that there was a false alarm in the situation just now.

To verify the inference, I'm going to do it again and add a mysterious parameter-u, which simply takes the zero time zone (UTC+0) as the standard output time. The input command is as follows:

Date-u-r 0date-u-r 60date-u-r 3600date-u-r 43200date-u-r 86400

These commands were gratified to give me the expected feedback output as quickly as possible:

From this moment on, although I feel that my skills have gone up a step again, at this time I think I should pause for a moment to recall the old days.

I soon got into the mood, thinking back to that summer in 1998, at 3: 00 a.m. on July 13, France's World Cup final France VS Brazil, a night that kept many people awake, but it was the first time I tried to watch a football match so late or so early, because I had always been a pupil with a regular schedule. Recalling this, I think I should do something, I actually want to check the time stamp of that night almost 20 years ago!

Date-> timestamp

So I quickly entered this familiar and distant date into the command:

Date-j 07130300 1998

The command gives an output:

The CST# France World Cup final starts at 03:00:00 Beijing time on Monday, July 13, 1998.

In the above command, I typed date-j 07130300 1998, where the-j argument means not to set the date string after him as the current system time, but to output it as the friendlier 03:00:00 CST on Monday, July 13, 1998. To put it simply, if I don't add the-j parameter, the date 07130300 1998 command will directly set the current time of my computer system to 3: 00 a.m. on July 13, 1998 summer, instead of printing that time on the screen.

But the string I provided is actually the format of the month, day, hour and year. 07 is July, 13 is 13, 03 is 3: 00 in the morning, 00 is 0, what is 1998? I know the exact date, and then input it into this date-j 07130300 1998 command, obviously not for its output to tell me that Monday, July 13, 1998, 03:00:00 CST is just the same date that is easier to read. I want to know the timestamp of this great time out of intense curiosity, so I have to tamper with it:

Date-j 07130300 1998 +% s

This command outputs only one number, which is the timestamp I want to know:

900270000

When I got the timestamp, I couldn't wait to use the following command:

Date-r 900270000

Once again, the command is output quickly:

Monday, July 13, 1998, 03:00:00 CST

After this series of operations, I not only learned the new parameter-j, but also reviewed the usage of the-r parameter again, more importantly, I completed the recollection of the good old days, which can be described as killing three birds with one stone.

Formatting

Although the previous commands are very slippery, but their output is a little lengthy, although very intelligently according to my Chinese user has given the highest treatment to Chinese output, but I feel very ordinary ~ now I urgently want to change the format of its output to show my unique personality and taste, so I started my operation again, and I am obviously still immersed in the recollection I just had. So I still intend to use 900270000, which represents the special timestamp of 3: 00 a.m. on July 13, 1998, to complete my operation:

Date-r 900270000 +% Y

It gave me a simple output in response:

1998

I was a little excited, as if I had found some tricks and continued to type:

Date-r 900270000 +% m

Once again, it gave me a more concise response:

07

I was even more excited and did not hesitate to enter:

Date-r 900270000 +% d

Sure enough, it didn't let me down and gave me the expected response:

thirteen

After three attempts, I got a taste of success, and I thought it was time to take advantage of the victory to pursue, so I decided to put% YMagol% mforce% d together. My sixth sense told me that I would succeed again:

Date-r 900270000 +% Y%m%d

As a result, it is obvious that the year, month and day appear on the screen together:

19980713

I am not satisfied, I want to get more sense of achievement, I want the output format to be more international, I continue to try:

Date-r 900270000 +% m/%d/%Y

As a result, it met my preliminary requirements:

07/13/1998

I am still not satisfied, because I think of the popular song "meet 98" sung by Wang Fei and Na Ying. I think I also want to show 98 instead of 1998. At that time, no one would say 1998, so I groped and tried again:

Date-r 900270000 +% m/%d/%y

Uppercase becomes lowercase, decay magical:

07/13/98

Sure enough, I was still not satisfied, thinking that if I could add a specific time later, I would stop, so I typed the following command in one go:

Date-r 900270000 +% m/%d/%y% H:%M:%S

When I thought that I was about to finish this pleasant operation trip, the reality gave me a taste of failure:

Date: illegal time format

It was a bit unpleasant for me to have an accident at the last minute, but with my solid foundation in CET-4, I still got some clues from the error message. combined with my years of work experience, I feel that it should be caused by my newly added format string% H:%M:%S in order to output minutes and seconds. I feel vaguely that the space before it caused the date command to mistakenly think that they were two separate strings when reading. At such times, it is customary to surround them in the legendary double quotation marks to indicate that they are a whole. So I rearranged the order:

Date-r 900270000 "+% m/%d/%y% H:%M:%S"

This time we can finally finish work, perfect output, perfect night, never go back 98:

07/13/98 03:00:00

Make a summary of commonly used command line date

The default format outputs the current date. Date +% Y%m%d%H%M%S

Custom format% Y%m%d%H%M%S output current date date-r 900270000

Default format output timestamp: 900270000 corresponding date date-r 900270000 +% Y%m%d%H%M%S

Custom format% Y%m%d%H%M%S output timestamp: 900270000 corresponding date date-j 07130300 1998

Default format output date string: 071303001998 corresponding date date-j 071303001998 +% Y%m%d%H%M%S

Custom format% Y%m%d%H%M%S output date string: 07130300 1998 corresponding date date-j 07130300 1998 +% s

Custom format% s output date string: 071303001998 timestamp format string meaning of the corresponding date

Note that case represents a completely different meaning.

% Y: year (Year)% y: year (year) last two digits% m: month (month)% d: day (day)% H: hour (Hour)% M: minute (Minute)% S: second (Second)% s: timestamp (stamp) date string default format

Month, day, hour and year (07 13 03 00 1998)

Those lost timestamps 900270000 1157040000 967737600 778348800 555087600 1430136000 1461758400 1493222400 1277913600

The above is all the content of the article "sample Analysis of time and timestamp in Linux/Unix". Thank you for reading! I believe we all have a certain understanding, hope to share the content to help you, if you want to learn more knowledge, welcome to follow the industry information channel!

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