What is unistdh header file?

The unistd.h header file is a standard header in C Programming that provides function declarations and macros for various system-level operations, primarily related to input and output (I/O) and POSIX operating system interfaces. It includes functions for file handling, process control, and system calls, among others. Common functions declared in unistd.h include read(), write(), close(), and fork(). It is primarily used in Unix-like operating systems.