File management

•       We will start our study with the functions available for the file I/O operations such as open a file, read & write a file, close a file and so on.

•       Most file IO operations are performed with the open, read, write, lseek and close system calls.

•       File descriptors

–      File descriptor is a non-negative integer representing the file opened in the kernel.

–      When is opened or newly created, the kernel returns a file descriptor to the process.

–      During read/write, the file is identified by the file descriptor that was returned by open()

System call	File Operation
open	open a file or device fs/open.c
creat	create a file or device
close	close a file descriptor
dup2	duplicate a file descriptor
dup	duplicate an open file descriptor
mmap	map files into memory (Only the PROT_READ protection flag is supported.)
munmap	unmap files from memory
pread	read from a file descriptor at a given offset
pwrite	write to a file descriptor at a given offset
read	read from a file descriptor
readv	read data from multiple buffers
write	write to a file descriptor
writev	write data from multiple buffers
lseek	reposition read/write file offset
llseek	move extended read/write file pointer
lstat	get file status
truncate	set a file to a specified length
ftruncate	set a file to a specified length
unlink	delete a name and possibly the file it refers to