1. How could you modify 3000test.c so it can report on whether two device files are equal without actually accessing the underlying devices? Specify the changes you would make to 3000test.c rather than doing this from scratch.

/* 3000test.c */ 

 2 

 3 

 4 

 5 

 6 

 7 #include  

 8 #include  

 9 #include  

10 #include  

11 #include  

12 #include  

13 #include  

14 #include  

15 #include  

16 

17 void report_error(char *error) 

18 { 

19 fprintf(stderr, "Error: %s ", error); 

20 

21 exit(-1); 

22 } 

23 

24 int main(int argc, char *argv[]) 

25 { 

26 struct stat statbuf; 

27 char *fn; 

28 int fd; 

29 size_t len, i, count; 

30 

31 char *data; 

32 

33 if (argc < 2) { 

34 if (argc < 1) { 

35 report_error("no command line"); 

36 fprintf(stderr, "Usage: %s  ", argv[0]); 

37 } else { 

38 report_error("Not enough arguments"); 

39 fprintf(stderr, "Usage: %s  ", argv[0]); 

40 } 

41 } 

42 

43 fn = argv[1]; 

44 

45 if (stat(fn, &statbuf)) { 

46 report_error(strerror(errno)); 

47 } 

48 

49 len = statbuf.st_size; 

50 printf("File %s:  ", fn); 

51 printf(" inode %ld ", statbuf.st_ino); 

52 printf(" length %ld ", len); 

53 

54 if (S_ISREG(statbuf.st_mode)) { 

55 fd = open(fn, O_RDONLY); 

56 if (fd == -1) { 

57 report_error(strerror(errno)); 

58 } 

59 data = (char *) mmap(NULL, len, 

60 PROT_READ, MAP_SHARED, fd, 0); 

61 if (data == MAP_FAILED) { 

62 report_error(strerror(errno)); 

63 } 

64 

65 count = 0; 

66 for (i=0; i 
67 if (data[i] == 'a') { 
 
68 count++; 
 
69 } 
 
70 } 
 
71 
 
72 printf(" a count %ld ", count); 
 
73 
 
74 if (munmap(data, len) == -1) { 
 
75 report_error(strerror(errno)); 
 
76 } 
 
77 close(fd); 
 
78 } 
 
79 
 
80 return 0; 
 
81 }