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1. Overview
In this tutorial, we’ll learn about system calls and their types.
2. What Is a System Call?
System calls are mechanisms that provide the operating system’s services to computer programs. Computer programs use system calls to request a service from the operating system’s kernel. Moreover, if a program requires a resource from the operating system, it needs to make a system call.
3. Types of System Calls
System calls provide many services to computer programs. They are categorized into five categories based on the services that they provide:
3.1. Process Control
Process control system calls are used to create and manage processes. For example:
- fork: a system call that creates a child process. The calling process will be the parent
- exit: it terminates the calling process
- exec: it’s used to execute a file, and it replaces the current process image with a new process image
- wait: suspends execution of the current process until one of its children terminates
3.2. File Management
File management system calls are used to manipulate files. Some of them are:
- open: opens a file specified by pathname. If the file doesn’t exist, it can create it.
- read: reads from a file descriptor into a buffer
- write: writes to a file descriptor from a buffer
- close: closes a file descriptor
3.3. Device Management
Device management system calls are used to manipulate or manage devices. For example, ioctl (input/output control) controls a device by sending a device-dependent request code.
3.4. Information Maintenance
Information maintenance system calls are used to manage and transfer information between the operating system and computer programs. For example, getpid is a system call that returns the process id (PID) of the calling process when it’s called by a program.
3.5. Communications
They’re used for communication between different processes. For example, pipe is a system call that creates a pipe, a unidirectional data channel that connects two processes.
4. Summary
In this tutorial, we learned about system calls and their types.