Read/write files for file I/O operations-based on Linux system file IO

1.

Read files that are already open

#include <unistd.h>ssize_t read (int fd,void *buf,size_t count);

Returns the number of bytes read, if it has returned 0 at the bottom of the file, an error returned-1

BUF is a pointer to a buffer that holds the data that will be read to the terminal, and count indicates the number of bytes to be read

2.

Write data to an open file

#include <unistd.h>ssize_t write (int fd,void *buf,size_t count);

Returns the number of bytes already written, with an error of 1

If you specify the O_append option, the end of the file is positioned before each write

Example:

1#include <stdio.h>2#include <sys/types.h>3#include <sys/stat.h>4#include <fcntl.h>5#include <unistd.h>6#include <string.h>7#include <stdlib.h>8 9 #defineFILENAME "Hello"Ten #defineBuf_size 80 One #defineFLAGS o_rdwr| O_append A intMainvoid) - { -     intcount; the     intFD; -     CharWrite_buff[buf_size]; -     Const Char*pathname=FILENAME; -     if((Fd=open (pathname,flags)) ==-1) +     { -printf"Error"); +Exit1); A     } atprintf"Ok,has opened file\n"); -printf"start to write:\n"); -  -scanf"%[^\n]", Write_buff); -  -Count=strlen (write_buff); in     if(Write (Fd,write_buff,count) ==-1) -     { toprintf"error to write\n"); +Exit0); -     } theprintf"OK have write to file\n"); *     return 0; $}

Read/write files for file I/O operations-based on Linux system file IO