fork system call

Explanation of the fork system call in C

The fork system call in C is used to create a new process by duplicating the existing process. Here is an explanation of each step involved in the fork system call:

  1. The fork function is called in the parent process. This function creates a new child process that is an exact copy of the parent process, including the code, data, and file descriptors.

  2. The operating system allocates a new process ID (PID) for the child process and sets up the necessary data structures to manage the child process.

  3. The child process is created and starts executing from the same point as the parent process. Both the parent and child processes continue executing the code after the fork function call.

  4. After the fork function call, the return value of the fork function is different for the parent and child processes. In the parent process, the return value is the PID of the child process, while in the child process, the return value is 0.

  5. The parent and child processes can now execute different sections of code based on the return value of the fork function. This allows for branching logic in the program to handle different tasks for the parent and child processes.

  6. The parent and child processes have separate memory spaces, but they share the same open file descriptors. This means that any changes made to a file descriptor in one process will be visible to the other process.

  7. The parent process can use the PID of the child process to perform various operations, such as waiting for the child process to terminate, sending signals to the child process, or collecting information about the child process.

  8. The child process can also execute its own code independently of the parent process. It can perform different tasks or execute a different program using the exec family of functions.

  9. The child process can terminate by reaching the end of its code or by calling the exit function. When the child process terminates, its exit status is made available to the parent process.

  10. The parent process can wait for the child process to terminate using the wait or waitpid functions. This allows the parent process to synchronize its execution with the child process and collect the exit status of the child process.

  11. Once the child process terminates, its resources are released by the operating system, and the parent process continues its execution.

Note: It's important to handle errors that may occur during the fork system call, such as when the system is unable to create a new process due to resource limitations.