Get filesystem creation date in C

I need to know the creation datetime of the filesystem on a disk (in a Linux machine) with C. I would like to avoid using shell commands, such as

tune2fs -l /dev/sdb2 | grep 'Filesystem created:' 

and make a parser.

Thanks

Answer

From a program coded in C (or in any language capable of calling C routines) you would use the stat(2) system call (or, with recent kernels and some file systems, the statx(2) one) to query the creation time of a given file (or directory). Of course, commands like ls(1) or stat(1) are using internally that stat(2) system calll.

There is no standard, and file system neutral, way to get the creation time of a given file system. That information is not always kept. I guess that FAT filesystems, or distributed file systems such as NFS, don’t keep that.

You might use stat(2) on the mount point of that file system.

The statfs(2) system call retrieves some filesystem information, but does not give any time stamps.

For ext4 file systems, see ext4(5) and use proc(5). You might parse /proc/mounts and some /proc/fs/ext4/*/ directory. The pseudofiles in /proc/ can be parsed quickly and usually won’t involve physical disk IO.

You could also work at the ext2/3/4 disk partition level, on an unmounted file ext[234] system, with a library like (or programs from) e2fsprogs. You should not access (even just read) a disk partition containing some file system if that file system is mounted.

^{(your question should give some motivation and context)}