[plug] speed: find vs ls

[Brad Campbell]

G'day all,

An observation while I'm still playing with my sizeable set of backup directories.
I've been adding a bit that creates a file of crc32s of the updated files, and then toying around with a script to crawl the drive and check them all.

I started using find to give me a list of dirs that contain the files. It was spending a *lot* of time just creating the list. In fact it spent more time looking for the files than the subsequent iteration and check of each one.
I must qualify that with the fact, I'm about 10 days into creating the crcs and most directories already have ~800 days worth of backups.

The script run with :
for j in `find . -maxdepth 2 -type f -name bkb.rhash.crc32 -printf "%h\n"` ; do

Checked 170 directories with 0 errors in 0:00:34:58

stracing find, it's dropping into each directory and performing a stat on every file. Some dirs have a *lot* of files.

I thought about trying a bit of globbing with ls instead, and blow me down if it wasn't "a bit faster".

The script run with :
for j in `ls ??????-????/bkb.rhash.crc32 2>/dev/null` ; do j=($dirname $j)

Checked 170 directories with 0 errors in 0:00:09:49

I know premature optimisation is the root of all evil, but this one might have been a case of "using the right tool".

Regards,
Brad
-- 
An expert is a person who has found out by his own painful
experience all the mistakes that one can make in a very
narrow field. - Niels Bohr