Create process fork

Name: fork
Role: Create a process
File: # include <unistd. h>
Definition: pid_t fork (void );

Note: fork () generates a new sub-process. Its sub-process copies the data and stack space of the parent process and inherits the user of the parent process.Code, Group code, environment variables, opened file code, working directory, and resource restrictions. Linux uses the copy-on-write (COW) technology. Only when one of the processes tries to modify the space to be copied can the real copy action be performed, because the inherited information is copied, it does not mean the same memory space. Therefore, the modifications made by the sub-process to these variables and the parent process are not synchronized. In addition, the child process does not inherit the file lock and unprocessed signals of the parent process. Note: Linux does not guarantee that the child process will be executed earlier or later than the parent process. ThereforeProgramPay attention to the occurrence of deadlocks or competitive conditions.

Return: If fork () is successful, the new Child Process Code (PID) is returned in the parent process, and 0 is returned in the newly created child process. If fork fails,-1 is returned. The cause of failure is stored in errno.

Error: The eagain memory is insufficient. The enomem memory is insufficient and the data structure space required by the core cannot be configured.

Code:
Pid_t PID;
PID = fork ()
If (pid = 0)
{
/* Child process */
}
Else if (pid> 0)
{
/* Parent process */
}
Else
{
/* Fork Error */
}