Shulou(Shulou.com)06/01 Report--

In this issue, the editor will bring you about how to debug C language skills under the Linux terminal. The article is rich in content and analyzes and describes for you from a professional point of view. I hope you can get something after reading this article.

1 、 strace

This feature is powerful, and you can see a lot of underlying calls, making it easy to analyze the problem:

For example:

[wangbin@localhost pas] $strace-p 10472Process 10472 attached-interrupt to quitfutex (0x4113be8, FUTEX_WAIT, 10482, NULLProcess 10472 detached

We can see that the process is deadlocked, so the strace command is very useful, especially for network programs.

2 、 tcpdump

When analyzing the fastcgi program, we use this command to view the tcp package:

[root@localhost] # tcpdump-I lo-s 1500 port 9000tcpdump: verbose output suppressed, use-v or-vv for full protocol decodelistening on lo, link-type EN10MB (Ethernet), capture size 1500 bytes15:23:16.901004 IP localhost.localdomain.50867 > localhost.localdomain.9000: s 3482201970 bytes15:23:16.901004 IP localhost.localdomain.50867 > localhost.localdomain.9000: s 3482201970 (0) win 32767 1515 bytes15:23:16.901004 IP localhost.localdomain.50867 2316.901025 IP localhost.localdomain.9000 > localhost.localdomain.50867: s 3473410857 win 3473410857 (0) ack 3482201971 win 32767 1523 Switzerland IP localhost.localdomain.50867 > localhost.localdomain.9000. Ack 1 win 256 15 ack 23 ack 16.901150 IP localhost.localdomain.50867 > localhost.localdomain.9000: P 1V 1377 (1376) ack 1 win 256 15 V 23 V 16.901170 IP localhost.localdomain.9000 > localhost.localdomain.50867:. Ack 1377 win 256 15 IP localhost.localdomain.9000 > localhost.localdomain.50867: P 1:97 (96) ack 1377 win 256 15 IP localhost.localdomain.9000 > localhost.localdomain.9000: 16.901222. Ack 97 win 256 15 ack 2316. 901236 IP localhost.localdomain.9000 > localhost.localdomain.50867: F 97:97 (0) ack 1377 win 256 15 ack 23 16. 901822 IP localhost.localdomain.50867 > localhost.localdomain.9000: F 1377 read 1377 (0) ack 98 win 256 15 IP localhost.localdomain.9000 > localhost.localdomain.50867:. Ack 1378 win 256

Through this command, we can find that port 9000 actively closes the connection, which means that it is ineffective to keep the connection on the other side.

3. Core file

This function is like the camera next to the cash machine, which can record the scenario when the program crashes, which is very useful for analyzing difficult problems, but with this, make sure the permissions are configured correctly.

4 、 gdb

Gdb-p process number, you can debug the executing process, the function is also very powerful. In other words, as long as you add-g to the online program and remove the optimization parameters, you can debug a process, such as the nginx process, when you go online.

5. Log file

This is the most commonly used and corny method, but it is still very useful for debugging.

The above is the editor for you to share how to debug the C language skills under the Linux terminal, if you happen to have similar doubts, you might as well refer to the above analysis to understand. If you want to know more about it, you are welcome to follow the industry information channel.

Welcome to subscribe "Shulou Technology Information " to get latest news, interesting things and hot topics in the IT industry, and controls the hottest and latest Internet news, technology news and IT industry trends.