文件IO

 1 #include <unistd.h>
 2 #include <sys/types.h>
 3 #include <sys/stat.h>
 4 #include <fcntl.h>
 5 #include <stdlib.h>
 6 #include <stdio.h>
 7 #include <string.h>
 8 void main(void)
 9 {
10     int fd,size,len;
11     char *buf="Hello! I‘m writing to this file!";
12     char buf_r[10];
13     len = strlen(buf);
14     /*调用open函数，以可读写的方式打开*/
15     if((fd = open("/tmp/hello.c", O_CREAT | O_TRUNC | O_RDWR, 0600 ))<0)
16     {
17         perror("open ERROR");
18         exit(1);
19     }
20     else
21     {
22         printf("Open file: hello.c %d\n",fd);
23         /*调用write函数，将buf中的内容写入到打开的文件中*/
24         if((size = write( fd, buf, len)) < 0)
25         {
26             perror("write ERROR");
27             exit(1);
28         }
29         else
30         {
31             printf("Write:%s\n",buf);
32             /*调用lsseek函数将文件指针移到文件起始，并读出文件中的10个字节*/
33             lseek( fd, 0, SEEK_SET);
34             if((size = read(fd, buf_r,10))<0)
35             {
36                 perror("read ERROR");
37                 exit(1);
38             }
39             else
40                 printf("read form file:%s\n",buf_r);
41         }
42     }
43     if( close(fd) < 0 )
44     {
45         perror("close:");
46         exit(1);
47     }
48     else
49     {
50         printf("Close hello.c\n");
51         exit(0);
52     }
53 }