A small BUG in Ubuntu for Advanced Programming in UNIX environment

In this book, the fork Standard & amp; 26684; formula is pid_tpid; if (pid = fork () in this book, the standard format when fork is used is

Pid_t pid;

If (pid = fork () <0) // error

{}

Else if (pid = 0) // sub-process

{}

Else // parent process

{}

When the code is written in the same format as above, the sub-process is always executed, and the sub-process is executed twice, but the parent process is not executed,

After self-analysis, a new sub-process is generated every time if (pid = fork () <0). The reason seems to be here, but no matter

What about the parent process.

Replace the above format

Pid_t pid;

Pid = fork ();

If (pid <0)

{}

Else if (pid = 0)

{}

Else

{}

My environment is ubuntu. I don't know if it is related to this ~~~