Linux View Log Common commands __linux

1. View Log common commands tail:-n is the display line number; the equivalent of the NL command; tail-100f test.log Real-time monitoring of 100-line logs

Tail-n test.log Query Log The last 10 lines of the tail;

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

Head

Contrary to the tail, tail is the number of rows after the log; examples are as follows:

Head-n test.log Query log file in the first 10 lines of log;

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

Cat

TAC is the reverse view, is the cat word reverse write;

Cat-n test.log |grep Log of "debug" query Keywords

2. Application Scene One: by line number View---Filter the log near the key word

1 cat-n test.log |grep "Debug" to get the line number of the key log

2 cat-n test.log |tail-n +92|head-n 20 Select the middle line where the keyword is located. Then look at the logs for the first 10 and 10 lines of this keyword:

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

Head-n 20 means to check the previous 20 records in the previous query results.

3. Application Scenario Two: query log based on date

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 log printed in the log, otherwise invalid;

First grep ' 2014-12-17 16:17:20 ' test.log to determine if the time point in the log

4. Application scenario Three: Log content is very much, print on the screen is not convenient to view

(1) using the more and less commands,

such as: Cat-n test.log |grep "Debug" |more so that pagination printing, by clicking the Space bar page

(2) Use >xxx.txt to save it to a file, and then you can pull down this file to analyze

such as: Cat-n test.log |grep "Debug" >debug.txt