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2025-04-08 Update From: SLTechnology News&Howtos shulou NAV: SLTechnology News&Howtos > Development >
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This article mainly introduces "how to view log files in Linux". In daily operation, I believe many people have doubts about how to view log files in Linux. The editor consulted all kinds of materials and sorted out simple and easy-to-use methods of operation. I hope it will be helpful to answer the doubts about "how to view log files in Linux". Next, please follow the editor to study!
1. View logs commonly used commands tail:
-n is the display line number; equivalent to the nl command; examples are as follows:
Tail-100f test.log real-time monitoring 100 lines of logs
Tail-n 10 test.log query the log of the last 10 lines at the end of the log
Tail-n + 10 test.log query all logs after 10 lines
Head:
Contrary to tail, tail refers to the number of lines of log after reading. Examples are as follows:
Head-n 10 test.log query the first 10 lines of logs in the log file
Head-n-10 test.log query log file all logs except the last 10 lines
Cat:
Tac is viewed in reverse order, which is the reverse of cat words. Examples are as follows:
Cat-n test.log | grep "debug" query the log of the keyword
\ 2. Application scenario 1: view by line number-filter out the log near the keyword 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 check the log of the first 10 lines and the last 10 lines of this keyword:
Tail-n + 92 represents the log after 92 lines of the query
Head-n 20 means to check the first 20 records in the previous query results.
\ 3. Application scenario 2: query the log sed-n'/ 2014-12-17 according to the date. 16-17-17 17-17 17-17 17-17 17-17-17 17-17 17-12-17 2014-12-17 16 sed-n'/ 17 17 17 12-17 17 17 12-17 17 17 12-17 2014-12-17 2014-12-17 14-12-17 14-12-17 2014-12-17 14-12-17 14-12-17 14-12-17 14-12-17 2014-12-17 14-12-17 query log log 2014-12-17 query log according to date
Special note: the above two dates must be the log printed in the log, otherwise it will be invalid
First grep '2014-12-17 16-16-14-17-17-17-17-17-17-16-17-17-17-17-16-17-17-17-16-17-17-17-16-17-12-16 to determine whether there is this time point in the log
4. Application scenario 3: the log contains a lot of content, so it is not easy to view it when printed on the screen
(1) use the more and less commands
For example: cat-n test.log | grep "debug" | more is printed in pages. Turn the page by clicking the spacebar.
(2) use > xxx.txt to save it to a file, and then you can pull down the file for analysis.
For example: cat-n test.log | grep "debug" > debug.txt
At this point, the study on "how to view log files in Linux" is over. I hope to be able to solve your doubts. The collocation of theory and practice can better help you learn, go and try it! If you want to continue to learn more related knowledge, please continue to follow the website, the editor will continue to work hard to bring you more practical articles!
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