The relationship between parent and child processes:
the difference:
1. The return value of the fork() function is different. In the parent process: >0. The returned child process ID. In the child process: ID=0.
2. The data in the pcb are different, the ID of the current process pid, the ID of the current parent process ppid, and the signal set
Common points:
In some states: the child process has just been created and has not yet performed any data writing operations.
-Data in user area
-File descriptor table
Are variables shared between parent and child processes?
-In the beginning, it was the same, shared. If the data is modified, it will not be shared.
-Sharing when reading (the child process is created, the two processes do not perform any writing operations), copying when writing,
GDB debugging
