When I running df -h I can see that in /dev I use 6M and the size is 40M , and Available size is 34M .
How can I get this information with c code?
From here:
Use the statvfs API:
// header for statvfs
#include <sys/statvfs.h>
and the prototype of the statvfs is
int statvfs(const char *path, struct statvfs *buf);
The results will be filled to the buf statvfs struct:
struct statvfs {
unsigned long f_bsize; /* filesystem block size */
unsigned long f_frsize; /* fragment size */
fsblkcnt_t f_blocks; /* size of fs in f_frsize units */
fsblkcnt_t f_bfree; /* # free blocks */
fsblkcnt_t f_bavail; /* # free blocks for unprivileged users */
fsfilcnt_t f_files; /* # inodes */
fsfilcnt_t f_ffree; /* # free inodes */
fsfilcnt_t f_favail; /* # free inodes for unprivileged users */
unsigned long f_fsid; /* filesystem ID */
unsigned long f_flag; /* mount flags */
unsigned long f_namemax; /* maximum filename length */
};
The return type is:
On success, zero is returned. On error, -1 is returned, and errno is set appropriately.
Also have a look at the man3 manpage of the statvfs command for more and detailed information.