File and Device Size

[haderach]

Hi,

i need to get the Size of a file (e.g. ~/files/hallo.txt) and the size of a deivce (e.g. /dev/sdb).


Is it possible to get both with the same functions?
Do i need to use specific Funktions for block or character devices?



Ps.:
Later i need to reed the whole file/device.
I need the file/device-size to show the progress.


Thx for all answers,

hd

[kermit]

Note that the linked man page is for Linux:

man 2 stat

[cpjust]

and here's the same thing on Windows: _stat()

[haderach]

I just copied the code out of the man-Page but:

 
printf("File size:                %lld bytes\n", (long long) sb.st_size);

always prints: "0" if u have a block device.


so i tried to lseek: but this alwas prinft "-1" if u have a block device?

 
fd = open(argv[1], 00);
size = lseek(fd, 0, SEEK_END);
close(fd);
printf("SIZE %d \n", size);

Am i doing something wrong?

[Adak]

For streams, this works, for devices requiring a file handle, lseek() should work, but it won't work on terminals and printers, according to my help file.

/*
 fseek   Repositions the file pointer of a stream.


 Syntax:
   int fseek(FILE *stream, long offset, int whence);

 Prototype in:
 stdio.h

 Remarks:
fseek sets the file pointer associated with stream to a new position
that is offset bytes from the file location given by whence.

For text mode streams, offset should be 0 or a value returned by
ftell.

whence must be one of the values 0, 1, or 2, which represent three
symbolic constants (defined in stdio.h) as follows:

   whence         ³ File location
 ======================================
   SEEK_SET   (0) ³ File beginning
   SEEK_CUR   (1) ³ Current file pointer position
   SEEK_END   (2) ³ End-of-file

fseek discards any character pushed back using ungetc.

fseek is used with stream I/O. For file handle I/O, use lseek.

After fseek, the next operation on an update file can be either input
or output.

 Return Value:
fseek returns 0 if the pointer is successfully moved. It returns a
nonzero on failure.

fseek can return a zero, indicating that the pointer has been moved
successfully, when in fact it has not been. This is because DOS,
which actually resets the pointer, does not verify the setting.

fseek returns an error code only on an unopened file or device.

 Portability:
fseek is available on all UNIX systems and is defined in ANSI C.

 See Also:
  fgetpos      fsetpos    lseek     setbuf
  fopen        ftell      rewind    tell

 Example:
 */
 #include <stdio.h>

 long filesize(FILE *stream);

 int main(void)
 {
    FILE *stream;

    stream = fopen("MYFILE.TXT", "w+");
    fprintf(stream, "This is a test");
    printf("Filesize of MYFILE.TXT is %ld bytes\n", filesize(stream));
    fclose(stream);
    return 0;
 }

 long filesize(FILE *stream)
 {
    long curpos, length;

    curpos = ftell(stream);
    fseek(stream, 0L, SEEK_END);
    length = ftell(stream);
    fseek(stream, curpos, SEEK_SET);
    return length;
 }

[haderach]

I am using Linux and i use it on an usbstick (/dev/sdb)

sudo ./fs /dev/sdb

File type: block device
I-node number: 3135617
Mode: 60660 (octal)
Link count: 1
Ownership: UID=0 GID=6
Preferred I/O block size: 4096 bytes
File size: 0 bytes
SIZE -1
Blocks allocated: 0
Last status change: Mon May 3 09:36:04 2010
Last file access: Mon May 3 09:36:06 2010
Last file modification: Mon May 3 09:36:04 2010

cat fs.c

#include <sys/types.h>

#include <time.h>
#include <stdio.h>
#include <stdlib.h>

#define __USE_LARGEFILE64
#define _LARGEFILE_SOURCE
#define _LARGEFILE64_SOURCE
#include <sys/stat.h>

        int
main(int argc, char *argv[])
{
    struct stat64 sb;
        int fd;
        unsigned long long size;

    if (argc != 2) {
        fprintf(stderr, "Usage: %s <pathname>\n", argv[0]);
        exit(EXIT_FAILURE);
    }

    if (stat64(argv[1], &sb) == -1) {
        perror("stat");
        exit(EXIT_FAILURE);
    }

    printf("File type:                ");

    switch (sb.st_mode & S_IFMT) {
        case S_IFBLK:  printf("block device\n");            break;
        case S_IFCHR:  printf("character device\n");        break;
        case S_IFDIR:  printf("directory\n");               break;
        case S_IFIFO:  printf("FIFO/pipe\n");               break;
        case S_IFLNK:  printf("symlink\n");                 break;
        case S_IFREG:  printf("regular file\n");            break;
        case S_IFSOCK: printf("socket\n");                  break;
        default:       printf("unknown?\n");                break;
    }

    printf("I-node number:            %ld\n", (long) sb.s

    printf("Mode:                     %lo (octal)\n",
            (unsigned long) sb.st_mode);

    printf("Link count:               %ld\n", (long) sb.s
    printf("Ownership:                UID=%ld   GID=%ld\n
            (long) sb.st_uid, (long) sb.st_gid);

    printf("Preferred I/O block size: %ld bytes\n",
            (long) sb.st_blksize);
    printf("File size:                %lld bytes\n",
            (long long) sb.st_size);


        fd = open64(argv[1], 00);
        size = lseek64(fd, 0, SEEK_END);
        close(fd);
        printf("SIZE %lld \n", (long long)size);


    printf("Blocks allocated:         %lld\n",
            (long long) sb.st_blocks);

    printf("Last status change:       %s", ctime(&sb.st_c
    printf("Last file access:         %s", ctime(&sb.st_a
    printf("Last file modification:   %s", ctime(&sb.st_m

    exit(EXIT_SUCCESS);
}

What am i doing wrong?

[Adak]

My example is only for reading a file - similar to fseek, but using the file handle, instead of a stream mode.

So I'm stumped.

[haderach]

Let me get the help file for lseek. I'm not a penguin-head.

lseek(2)


perhaps lseek isnt the answer to my problem but pv uses it :

 77       if (S_ISBLK(sb.st_mode)) {
 78             /*
 79              * Get the size of block devices by opening
 80              * them and seeking to the end.
 81              */
 82             if (strcmp(opts->argv[i], "-") == 0) {
 83                 fd = open64("/dev/stdin", O_RDONLY);
 84             } else {
 85                 fd = open64(opts->argv[i], O_RDONLY);
 86             }
 87             if (fd >= 0) {
 88                 opts->size += lseek64(fd, 0, SEEK_END);
 89                 close(fd);
 90             }
 91         } else if (S_ISREG(sb.st_mode)) {
 92             opts->size += sb.st_size;
 93         } else {
 94             opts->size = 0;
 95         }

[haderach]

Solution:

  1 #include <fcntl.h>
  2 #include <linux/fs.h>
  3 #include <stdio.h>
  4 
  5 
  6 main(int argc, char **argv)
  7 {
  8   int fd;
  9   unsigned long numblocks=0;
 10 
 11   fd = open(argv[1], O_RDONLY);
 12   ioctl(fd, BLKGETSIZE64, &numblocks);
 13   close(fd);
 14   printf("Number of bytes: %lu, this makes %.3f GB\n",
 15      numblocks,
 16      (double)numblocks / (1024 * 1024 * 1024));
 17 }

Ps.: would be nice if someone can tell me why it is not working with lseek.


THX2all

[tabstop]

The most definitive person to ask why it is not working is your machine.

numblocks = lseek(fd);
if (numblocks == -1) {
    perror("Lseek didn't work because");
}