详解C语言中write函数

#include <stdio.h> 
        #include <stdlib.h> 
        #include <fcntl.h> 
        #include <sys\stat.h> 
        #include <io.h> 
        #include <string.h> 
        int  
        main( 
        void 
        ) 
        { 
        int  
        *handle;  
        char  
        string[40]; 
        int  
        length, res; 
        /* Create a file named "TEST.$$$" in the current directory and write a string to it. If "TEST.$$$" already exists, it will be overwritten. */ 
        if  
        ((handle = open( 
        "TEST.$$$" 
        , O_WRONLY | O_CREAT | O_TRUNC, S_IREAD | S_IWRITE)) == -1) 
        { 
        printf 
        ( 
        "Error opening file.\n" 
        ); 
        exit 
        (1); 
        } 
        strcpy 
        (string,  
        "Hello, world!\n" 
        ); 
        length =  
        strlen 
        (string); 
        if  
        ((res = write(handle, string, length)) != length) 
        { 
        printf 
        ( 
        "Error writing to the file.\n" 
        ); 
        exit 
        (1); 
        } 
        printf 
        ( 
        "Wrote %d bytes to the file.\n" 
        , res); 
        close(handle);  
        return  
        0;  
        } 

ssize_t read( int  fd, void   * buf,size_t nbyte) 

ssize_t write( int  fd, const   void   * buf,size_t nbytes)