How do you determine a file's attributes?


The file attributes are stored in the find_t.attrib structure member. This structure member is a single character, and each file attribute is represented by a single bit. Here is a list of the valid DOS file attributes:

Value   Description   Constant
0x00 - Normal - (none)
0x01 - Read Only - FA_RDONLY
0x02 - Hidden File - FA_HIDDEN
0x04 - System File - FA_SYSTEM
0x08 - Volume Label - FA_LABEL
0x10 - Subdirectory - FA_DIREC
0x20 - Archive File - FA_ARCHIVE

To determine the file's attributes, you check which bits are turned on and map them corresponding to the preceding table. For example, a read-only hidden system file will have the first, second, and third bits turned on. A "normal" file will have none of the bits turned on. To determine whether a particular bit is turned on, you do a bit-wise AND with the bit's constant representation.

The following program uses this technique to print a file's attributes:

#include <stdio.h>
#include <direct.h>
#include <dos.h>
#include <malloc.h>
#include <memory.h>
#include <string.h>
typedef struct find_t FILE_BLOCK;
void main(void);
void main(void)
     FILE_BLOCK f_block;  /* Define the find_t structure variable */
     int ret_code;     /* Define a variable to store the return codes */
     printf("\nDirectory listing of all files in this directory:\n\n");
     /* Use the "*.*" file mask and the 0xFF attribute mask to list
        all files in the directory, including system files, hidden
        files, and subdirectory names. */
     ret_code = _dos_findfirst("*.*", 0xFF, &f_block);
     /* The _dos_findfirst() function returns a 0 when
        it is successful and has found a valid filename
        in the directory. */
     while (ret_code == 0)
          /* Print the file's name */
          printf("%-12s  ",;
          /* Print the read-only attribute */
          printf("%s ", (f_block.attrib & FA_RDONLY) ? "R" : ".");
          /* Print the hidden attribute */
          printf("%s ", (f_block.attrib & FA_HIDDEN) ? "H" : ".");
          /* Print the system attribute */
          printf("%s ", (f_block.attrib & FA_SYSTEM) ? "S" : ".");
          /* Print the directory attribute */
          printf("%s ", (f_block.attrib & FA_DIREC)  ? "D" : ".");
          /* Print the archive attribute */
          printf("%s\n", (f_block.attrib & FA_ARCH)  ? "A" : ".");
          /* Use the _dos_findnext() function to look
             for the next file in the directory. */
          ret_code = _dos_findnext(&f_block);
     printf("\nEnd of directory listing.\n");


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