How to count the total number of files/folders on a system?

Since file / folder names can contain newlines:

sudo find / -type f -printf '.' | wc -c
sudo find / -type d -printf '.' | wc -c

This will count any file / folder in the current / directory. But as muru points out you might want to exclude virtual / other filesystems from the count (the following will exclude any other mounted filesystem):

find / -xdev -type f -printf '.' | wc -c
find / -xdev -type d -printf '.' | wc -c

• sudo find / -type f -printf '.': prints a dot for each file in /;
• sudo find / -type d -printf '.': prints a dot for each folder in /;
• wc -c: counts the number of characters.

Here's an example of how not taking care of newlines in file / folder names may break other methods such as e.g. find / -type f | wc -l and how using find / -type f -printf '.' | wc -c actually makes it right:

% ls
% touch "file
\`dquote> with newline"
% find . -type f | wc -l
2
% find . -type f -printf '.' | wc -c
1

If STDOUT is not a terminal, find will print each file / folder name literally; this means that a file / folder name containing a newline will be printed across two different lines, and that wc -l will count two lines for a single file / folder, ultimately printing a result off by one.

1 method would be

sudo find / -type f | wc -l
sudo find / -type d | wc -l

(sudo to prevent accessing errors)

f for files, d for directories.

The /proc/ filesystem will error out but I do not consider those files ;)

If you really want the total number of objects in your filesystems, use df -i to count inodes. You won't get the breakdown between directories and plain files, but on the plus side it runs near-instantly. The total number of used inodes is something filesystems already track.

If you want to use one of the find-based suggestions, don't just run it on /. Use find -xdev on a list of mount points generated by something like findmnt --list -v -U -t xfs,ext3,ext4,btrfs,vfat,ntfs -o TARGET or something. That doesn't exclude bind mounts, though, so files under bind mounts will get counted twice. findmnt is pretty cool.

Also, surely there's a straightforward way to list all your "disk" mounts without having to list explicit filesystem types, but I'm not sure exactly what.

As suggested by another answer, use find -printf . | wc -c to avoid any possible problems counting funny characters in filenames. Use -not -type d to count non-directory files. (You don't want to exclude your symlinks, do you?)

sudo find / -type f | wc -l

will tell you the number of regular files on your system, and

sudo find / -type d | wc -l

the number of folders.

Using zsh:

As root, for regular files:

files=( /**/*(.D) )

this will take all the regular files including the ones starting with a . into the array files, now we can simply count the number of elements of the array:

echo $#files

this will handle all the edge cases e.g. unusual file names.

Similarly for directories:

dirs=( /**/*(/D) )
echo $#dirs