How do I get the file size of a large (> 4 GB) file?

Question

How can I get the file size of a file in C when the file size is greater than 4gb?

ftell returns a 4 byte signed long, limiting it to two bytes. stat has a variable of type off_t which is also 4 bytes (not sure of sign), so at most it can tell me the size of a 4gb file.

What if the file is larger than 4 gb?

here: http://stackoverflow.com/questions/1035657/seeking-and-reading-large-files-in-a-linux-c-application — Drakosha, May 10 '10 at 04:43
Can this help you: http://stackoverflow.com/questions/238603/how-can-i-get-a-files-size-in-c — Boris, May 10 '10 at 04:43

score 2 · Accepted Answer · answered May 10 '10 at 04:53

2

On Linux with glibc, ftell returns an off_t; depending on the flags off_t may be 32 bit or may be 64 bit.

On Linux, you can get the appropriate flags to have a 64 bit off_t by doing getconf LFS_CFLAGS (LFS stands for large-file-support).

answered May 10 '10 at 04:53

R Samuel Klatchko

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glibc documentation shows `ftell` returning `long int` and `ftello` returning `off_t`. http://www.gnu.org/software/libc/manual/html_node/File-Positioning.html – Gavin Smith Mar 20 '14 at 02:26

score 2 · Answer 2 · answered May 10 '10 at 05:11

2

On Windows, GetFileSize[Ex] is what you use.

answered May 10 '10 at 05:11

Alex Budovski

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score 1 · Answer 3 · answered May 10 '10 at 05:14

1

try

#define _LARGEFILE64_SOURCE 1
#define _FILE_OFFSET_BITS 64

i think that increases the size of off_t to 64 bits on some operating systems

answered May 10 '10 at 05:14

Jay

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How do I get the file size of a large (> 4 GB) file?

3 Answers3