写操作
 1 #include <stdio.h>

 #include <stdlib.h>

 #include <fcntl.h>

 #include <unistd.h>

 void error_handling(char* message);

 int main()

 {

     int fd;

     char buf[] = "let's go!";

     fd = open("1.txt",O_CREAT|O_WRONLY);

     if(fd == -)

         error_handling("open error");

     printf("file descriptor:%d \n",fd);

     if(write(fd,buf,sizeof(buf)) == -)

         error_handling("write error");

     close(fd);

     return ;

 }

 void error_handling(char* message)

 {

     fputs(message,stderr);

     fputc('\n',stderr);

     exit();

 }

写操作 
1 #include <stdio.h>

 #include <stdlib.h>

 #include <unistd.h>

 #include <fcntl.h>

 void error_handling(char* message);

 int main()

 {

     int fd;

     char buf[];

     fd = open("1.txt",O_RDONLY);

     if(fd == -)

         error_handling("open error");

     printf("file description;%d\n",fd);

     if(read(fd,buf,sizeof(buf)-)==-)

         error_handling("read error");

     printf("file data:%s\n",buf);

     close(fd);

     return ;

 }

 void error_handling(char* message)

 {

     fputs(message,stderr);

     fputc('\n',stderr);

     exit();

 }