Sams Teach Yourself C in 21 Days

Using Disk Files 469

16

27: int c;

28:

29: /* Open the source file for reading in binary mode. */

30:

31: if ( ( fold = fopen( oldname, “rb” ) ) == NULL )

32: return -1;

33:

34: /* Open the destination file for writing in binary mode. */

35:

36: if ( ( fnew = fopen( newname, “wb” ) ) == NULL )

37: {

38: fclose ( fold );

39: return -1;

40: }

41:

42: /* Read one byte at a time from the source; if end of file */

43: /* has not been reached, write the byte to the */

44: /* destination. */

45:

46: while (1)

47: {

48: c = fgetc( fold );

49:

50: if ( !feof( fold ) )

51: fputc( c, fnew );

52: else

53: break;

54: }

55:

56: fclose ( fnew );

57: fclose ( fold );

58:

59: return 0;

60: }

Enter source file: list1610.c

Enter destination file: tmpfile.c

Copy operation successful

The function copy_file()works perfectly well, letting you copy anything from

a small text file to a huge program file. It does have limitations, however. If the

destination file already exists, the function deletes it without asking. A good program-

ming exercise for you is to modify copy_file()to check whether the destination file

already exists, and then query the user as to whether the old file should be overwritten.

LISTING16.10 continued

INPUT/

OUTPUT

ANALYSIS

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