ssize_t read(int fd, void *buffer, size_t count); ssize_t write(int fd, void *buffer, size_t count);
These syscalls attempts to read or write up to passed count from the passed file descriptor.
On files that support seeking, the operation commences at the file offset, and the file offset is incremented by the number of bytes read or written. If the file offset is at or past the end of file, no bytes are read or written, and the operation returns zero.
These syscalls returns the number of bytes operated on, or -1 on
failure. errno is to be set to:
EBADF: Bad file descriptor.
EFAULT: The passed buffer is not accessible.
EINVAL: The passed fd is not suitable for the operation.
EFBIG: When writing, the issued write would surpass the process
file size limit.
EIO: The requested operation failed at the device level.