Linux View Log Method summary (1)

Note: The log file is: Test.log

1.tail-f Test.log

View the currently printed log (this method is always known!) There is a limit to the length of the printout. ）

The following are collected online:

2. You must first understand the two most basic commands:

1. tail -n  10  Test.log   Log at the end of the last 10 lines of the query log;

   Tail-n +10 test.log    queries all logs after 10 rows;

   Head-n 10  test.log   query log file for the first 10 lines of the log;

   Head-n -10  test.log   query log file except for all other logs in the last 10 lines;

2. Scene 1: View---By line number filter out the log near the keyword

   Because we usually get very few logs with grep, we need to look at the logs nearby.

   I do this, first: cat-n test.log |grep "terrain"   get the line number of the critical log

3. <3> the line number where the "terrain" keyword is located is 102 rows. At this point, if I want to see the logs for the first 10 rows and the last 10 lines of this keyword:

   Cat- n test.log |tail-n +92|head-n

   Tail-n +92 means that the log after 92 rows is queried

   Head-n 20 indicates that the previous query results are checked for the first 20 records

4. Scenario 2: So what's the date??  usually we really need to find the log at the specified time.

   Sed-n '/2014-12-17 16:17:20/,/ 2014-12-17 16:17:36/p '   Test.log

   Special note: The above two dates must be the one printed in the log, otherwise invalid.

For date printing, you can first grep ' 2014-12-17 16:17:20 ' test.log to determine if there is a point in the log to ensure that the 4th step can get the log

This is a very useful command for querying logs based on time periods.

If we look for a lot of logs, printing on the screen is not easy to view, there are two ways:

(1) Use the more and less commands, such as: Cat-n test.log |grep "terrain" |more so that the page printing, by clicking the Space bar to page

(2) using >xxx.txt to save it to a file, you can pull down this file analysis. For example:

Cat-n test.log |grep "Terrain" >xxx.txt

Linux View Log Method summary (1)