低级文件操作实例代码

01	#include <stdio.h>

02	#include <stdlib.h>

03	#include <fcntl.h>

04	#include <unistd.h>

05	#include <string.h>

06	#include <sys/types.h>

07

08

09	#define FILE_TXT "sf.txt"

10	#define FILE_BIN "sf.bin"

11

12	typedef struct student

13

{

14

int id;

15	char name[16];

16	double score;

17

}student;

18

19	int main(void)

20

{

21	int fd_txt, fd_bin;

22	int i, result, len;

23	long offset = 0;

24	student stu_txt[3], stu_bin[3];

25	char buf[64];

26

27	//打开二进制文件进行读

28	fd_bin = open(FILE_BIN, O_RDONLY);

29	if(fd_bin<0)

30

{//文件打开失败

31	perror("open");

32

exit(-1);

33

}

34

35	memset(stu_bin, 0, sizeof stu_bin); //清空数据

36	for(i=0; i<sizeof(stu_bin)/sizeof(stu_bin[0]); i++)

37

{

38	result = read(fd_bin, &stu_bin[i], sizeof(stu_bin[i]));

39	if(result != sizeof(stu_bin[i]))

40

{

41	printf("read error.");

42

break;

43

}

44

}

45	printf("binary file read result:\n");

46	for(i=0; i<sizeof(stu_bin)/sizeof(stu_bin[0]); i++)

47

{

48	printf("%d %s %f\n",

49	stu_bin[i].id,

50	stu_bin[i].name,

51	stu_bin[i].score);

52

}

53	close(fd_bin);

54

55	//打开文本文件进行读

56	fd_txt = open(FILE_TXT, O_RDONLY);

57	if( fd_txt < 0)

58

{//文件打开失败

59	perror("open");

60

exit(-1);

61

}

62	memset(stu_txt, 0, sizeof(stu_txt));

63	offset = 0;

64	for(i=0; i<sizeof(stu_txt)/sizeof(stu_txt[0]); i++)

65

{

66

char * p;

67	memset(buf, 0, sizeof(buf));

68	result = pread(fd_txt, buf, sizeof(buf), offset);

69	if(result <= 0)

70

break;

71	sscanf(buf, "%d %s %lf",

72	&stu_txt[i].id,

73	stu_txt[i].name,

74	&stu_txt[i].score);

75

76	p = strstr(buf, "\n");

77

if(p)

78

*p = 0;

79	offset += strlen(buf) + 1;

80

}

81	printf("text file read result:\n");

82	for(i=0; i<sizeof(stu_txt)/sizeof(stu_txt[0]); i++)

83

{

84	printf("%d %s %f\n",

85	stu_txt[i].id,

86	stu_txt[i].name,

87	stu_txt[i].score);

88

}

89	close(fd_txt);

90

91

return 0;

92

}