The size of the directory (as seen with
ls -ld /var/lib/php/sessions) can give an indication. If it's small, there aren't many files. If it's large, there may be many entries in there, or there may have been many in the past.
Listing the content, as long as you don't
stat individual files, shouldn't take a lot much longer than reading a file the same size.
What might happen is that you have an alias for
ls that does
ls -F or
ls --color. Those options cause an
lstat system call to be performed on every file to see for instance if they are a file or directory.
You'll also want to make sure that you list dot files and that you leave the file list unsorted. For that, run:
command ls -f /var/lib/php/sessions | wc -l
Provided not too many filenames have newline characters, that should give you a good estimate.
$ ls -lhd 1
drwxr-xr-x 2 chazelas chazelas 69M Aug 15 20:02 1/
$ time ls -f 1 | wc -l
ls -f 1 0.68s user 1.20s system 99% cpu 1.881 total
wc -l 0.00s user 0.18s system 9% cpu 1.880 total
$ time ls -F 1 | wc -l
You can also deduce the number of files there by subtracting the number of unique files elsewhere in the file system from the number of used inodes in the output of
For instance, if the file system is mounted on
/var, with GNU
find /var -xdev -path /var/lib/php/sessions -prune -o \
-printf '%i\n' | sort -u | wc -l
To find the number of files not in /var/lib/php/sessions. If you subtract that to the
IUsed field in the output of
df -i /var, you'll get an approximation (because some special inodes are not linked to any directory in a typical ext file system) of the number of files linked to
/var/lib/php/sessions that are not otherwise linked anywhere else (note that /var/lib/php/sessions could very well contain one billion entries for the same file (well actually the maximum number of links on a file is going to be much lower than that on most filesystems), so that method is not fool-proof).
Note that if reading the directory content should be relatively fast, removing files can be painfully slow.
rm -r, when removing files, first lists the directory content, and then calls
unlink() for every file. And for every file, the system has to lookup the file in that huge directory, which if it's not hashed can be very expensive.