Low-Level I/O M3 Test

Low-Level I/O M3 Test

1. The low-level open() function, when succeeded, returns:

   • an int as an error code
   • an int as a file descriptor
   • a pointer to an error code
   • a pointer to a file descriptor

2. The readlink() function:

   • gets the name of a file pointed to by the link
   • gets all names of the link
   • reads a file pointer to by the link
   • gets all names of the file pointed to by the link

3. A descriptor with a value equal to 0:

   • is connected to stderr
   • is connected to stdin
   • is not connected and may be freely used
   • is connected to stdout

4. What should be placed instead of <?> to make the following snippet work properly?

   int fd = open("input", o_WRONLY);
   if(<?> ) {
       puts("File could not be open");
       exit(1);
   }

   • fd > 0
   • fd < 0
   • fd == NULL
   • fd == 0

5. An “endline translation” occurs:

   • when the file is being created
   • when the file is opened with an O_TEXT flag
   • when the file is opened with O_TEXT and O_BINARY flags ORed (|)together
   • when the file is opened with an O_BINARY flag

6. An EBADF (Bad file descriptor) error may occur during the invocation:

   • open(fname, O_RDWR)
   • unlink("file.txt");
   • readlink("file.txt", namebuff, sizeof(namebuff));
   • read(fd, buff, 100);

7. To create a link in an MS Windows environment, you may use the function named:

   • CreateSymbolicLink()
   • symlink()
   • createsymlink()
   • makesymlink()

8. Which snippet will you use to delete the file name file ?

   • int fd = open("file",O_RDWR); unlink(fd); close(fd);
   • open("file", O_DELETE);
   • FILE *f = fopen("file","rw"); unlink(f); fclose(f);
   • unlink("file");

9. The O_CREATE flag, used by the open() function, has the following effect:

   • if the file does not exit, it will be created 
   • if the file exists, it will be truncated to zero
   • if the file exists, it will be erased and created again
   • if the  file does not exists, the open() function will fail

10. The fcntl() function

    • is able to change all of the access modes specified during the open() function invocation
    • must not be used when it comes to a regular file’s access modes
    • is not able to change the access mode specified during the  open() function invocation
    • is able to change some of the access modes specified during the open() function invocation

11. The st_ino filed of the struct stat :

    • is always -1 in MS Windows
    • is emulated in MS Windows 
    • has no meaning in MS Windows
    • if fully supported in MS Windows

12. The lseek(fd, 0, seek_CUB) invocation sets the file pointer to:

    • the file’s beginning 
    • the same place as before invocation
    • a random position 
    • the file’s end

13. The so-called EPOCH time is the number of seconds elapsed from 00:00:00UTC, 1 January:

    • 1990
    • 1970
    • 1960
    • 1980

14. The dprintf() funciton is designed to:

    • print the formatted strings to two streams at the same time
    • print doubles instead of floats
    • use a file descriptor instead of the FILE * pointer
    • deleted stream content

15. The st_mode field of struct stat in an MS Windows environment determines the state of an “executable” attribute:

    • using the owner’s name 
    • using the owner’s permission
    • using the file’s permission
    • using the file’s name

16. To write all the elements of the array declared below, you may use the invocation:

    double vec[3] = {-1., 1., 0};

    • write(fh, vec, sizeof(vec));
    • write(fh, vec, 3);
    • write(fh, sizeof(vec), vec);
    • write(fh, 3, vec);

17. The close() function:

    • is of the void type
    • may not succeed
    • does not return any useful value 
    • always succeeds

18. How many bytes will the following program write to a file, assuming that the code is compiled by a CL compiler and successfully run on MS Windows?

    #include <io.h>
    #include <fcntl.h>
    int main(void) {
         char buff[] = "ABC\n";
         int fd = open("file", O_WRONLY | O_CREATE | O_TEXT);
         write(fd, buff, strlen(buff));
         close(fd);
         return 0;
    }

    • three
    • zero
    • five
    • four

19. The fileno() function:

    • create a new file descriptor
    • extracts a file descriptor from the given FILE structure
    • counts all currently open file descriptor
    • puts a file descriptor into the given FILE structure

20. The stat() function:

    • is partially supported in non-Unix operating systems
    • is not accessible in non-Unix operating systems
    • is full supported in all operating systems
    • is named Stat(0 in non-Unix operating systems