How can I find the number of files on a filesystem?

Question

I want to know how many files I have on my filesystem. I know I can do something like this:

find / -type f | wc -l

This seems highly inefficient. What I'd really like is to do is find the total number of unique inodes that are considered a 'file'.

Is there a better way?

Note:

I would like to do this because I am developing a file synchronization program, and I would like to do some statistical analysis (like how many files the average user has total vs how many files are on the system). I don't, however, need to know anything about those files, just that they exist (paths don't matter at all). I would especially like to know this info for each mounted filesystem (and it's associated mount point).

Solution 1

The --inodes option to df will tell you how many inodes are reserved for use. For example:

$ df --inodes / /home
Filesystem            Inodes   IUsed   IFree IUse% Mounted on
/dev/sda1            3981312  641704 3339608   17% /
/dev/sda8            30588928  332207 30256721    2% /home
$ sudo find / -xdev -print | wc -l
642070
$ sudo find /home -print | wc -l
332158
$ sudo find /home -type f -print | wc -l
284204

Notice that the number of entries returned from find is greater than IUsed for the root (/) filesystem, but is less for /home. But both are within 0.0005%. The reason for the discrepancies is because of hard links and similar situations.

Remember that directories, symlinks, UNIX domain sockets and named pipes are all 'files' as it relates to the filesystem. So using find -type f flag is wildly inaccurate, from a statistical viewpoint.

Solution 2

Use statvfs(), and calculate f_files - f_ffree.

Comments

[zilitron]

I think this is what I'm looking for. Is there any way to find out how many of each type of file there is? This isn't directly needed by my application, but could be useful knowledge.

[Arcege]

Not without inspecting the inodes of each file in the filesystem, which would be about the same as doing the find.

[zilitron]

Does df understand most filesystems (ext2-4, ntfs, fat, reiserfs, etc)?

[Arcege]

It would understand any filesystem type that could be mounted. Some filesystem types do not have inodes (for example, fat); df would display the total number of inodes as 0 on those filesystems. Other types should show the underlying filesystem's inode stats.

[n0pe]

Would you have to redirect errors to /dev/null seeing as you would get lines warning you that files in /proc are "virtual"?

[Arcege]

The -xdev option in find would prevent traversing into the /proc and /sys filesystems. With the sudo, the commands have enough read access to directories and inodes to not generate errors.