Linux: Getting Mount Point Utilization from /proc?

Question

I know I can get mount point utilization using command line tools like df and doing something like the following:

popen("df -h /var/log | awk '{if($1==\"tmpfs\") print $5}'","r")

where the fifth column is the usage percentage.

What I want to know is if there is a way to access mount point utilization from /proc/, such as /proc/mounts. I feel that getting this information from /proc/ would be a quicker and more efficient solution than using df and awk to parse out the usage. I've searched mntent.h but couldn't find anything promising there either. Any ideas?

Answer 1

You probably want the statfs(2) syscall (it does not use /proc/). You probably would use it thru statvfs(3) Posix function.

Notice that the /proc/ filesystem (and also /sys/ ...) contains pseudo-files which are generated by the kernel on demand without any IO. See proc(5). You could read sequentially /proc/self/mounts and/or /proc/self/mountstats and/or appropriate files under /proc/fs/ and/or /sys/ (such as some files in /proc/fs/ext4/sda1/ or even in /sys/block/sda/sda1/ for my desktop computer ; it would be different on yours ....)

Perhaps systemd is also able to give such information, but I don't know it enough.