JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD B.Tech IV Year REAL TIME SYSTEMS Previous Question Paper (July/August - 2022 - R18)

File I/O system calls are the interface between user-level applications and the operating system kernel, allowing processes to perform operations on files. The following are five essential system calls:

1. open(): Used to establish a connection between a file and a process. It returns a file descriptor, which is a non-negative integer used for subsequent operations. Example:
   fd = open("file.txt", O_RDONLY);
2. read(): Reads a specified number of bytes from the file associated with the file descriptor into a buffer. It returns the number of bytes actually read. Example:
   n = read(fd, buffer, 1024);
3. write(): Writes data from a buffer into the file associated with the file descriptor. It returns the number of bytes successfully written. Example:
   n = write(fd, "Hello", 5);
4. lseek(): Repositions the file offset of the open file description associated with the file descriptor, allowing for random access or non-sequential reading/writing. Example:
   lseek(fd, 10, SEEK_SET);
5. close(): Terminates the association between the file descriptor and the file, releasing the resources held by the kernel for that file. Example:
   close(fd);