fork and printf

fork() is non-deterministic, and sometime this can be a real problem. To solve this kind of problem, you may need to rely on your previous experience.

One day when experimenting on fork(), I got a strange print message.

I was surprised and could not figure out why for a while. Since I am using CLion and WSL 2, I soon realized that maybe it was the fault of CLion. So I ran the executable myself. A different print message came to my eyes.

No wonder.

After a long time of thinking, I related to procedures of how shells work. When you type in a command and hit enter, the shell calls fork() to create a new child process to run the command. The control soon returns to the shell after the command program is finished. However, if the command program creates a subprocess, and the subprocess is still running even if the main process has already returned, this can happen.

In order to check my assumption, I decided to wait() for the child process to finish. And this time it worked perfectly.

Be careful of the environment you are using. Search the database in your brain.