find vs. locate

There are the commands find and locate to search for files on the disk.

I know that find recursively processes all needed subdirectories to search files and therefore is slow but up-to-date, whereas locate uses a database that gets updated every now and then (when exactly?) to quickly show results which might be outdated though.

Are there any other differences? In which situations would one prefer the one or the other? And when does the locate database get updated usually?

locate is really only good for finding files and displaying them to humans. You can do a few things with it, but I wouldn't trust it enough to parse and —as you say— it's impossible to guarantee the state of the internal database, more so because it's only scheduled to run from /etc/cron.daily/mlocate, once a day!

find is live. It filters, excludes, executes. It's suitable for parsing. It can output relative paths. It can output full paths. It can do things based on attributes, not just names.

locate certainly has a place in my toolbox but it's usually right at the bottom as a last-ditch effort to find something. It's easier than find too.

As much as I like Oli (which is a lot!) I disagree with him on the find command. I don't like it.

find command takes over three minutes

Take for example this simple command:

$ time find / -type f -name "mail-transport-agent.target"
find: ‘/lost+found’: Permission denied
find: ‘/etc/ssmtp’: Permission denied
find: ‘/etc/ssl/private’: Permission denied
    (... SNIP ...)
find: ‘/run/user/997’: Permission denied
find: ‘/run/sudo’: Permission denied
find: ‘/run/systemd/inaccessible’: Permission denied

real    3m40.589s
user    0m4.156s
sys     0m8.874s

It takes over three minutes for find to search everything starting from /. By default reams of error messages appear and you must search through them to find what you are looking for. Still it is better than grep to search the whole drive for a string which takes 53 hours: `grep`ing all files for a string takes a long time

I know I can fiddle with the find command's parameters to make it work better but the point here is the amount of time it takes to run.

locate command takes less than a second

Now let's use locate:

$ time locate mail-transport-agent.target
/lib/systemd/system/mail-transport-agent.target

real    0m0.816s
user    0m0.792s
sys     0m0.024s

The locate command takes less than a second!

updatedb only run once a day by default

It is true the updatedb command which updates the locate database is only run once a day by default. You can run it manually before searching for files just added by using:

$ time sudo updatedb

real    0m3.460s
user    0m0.503s
sys     0m1.167s

Although this will take 3 seconds, it's small in comparison to find command's 3+ minutes.

I've updated my sudo crontab -e to include the line at the bottom:

# m h  dom mon dow   command
  0 0  1   *   *     /bin/journalctl --vacuum-size=200M
*/5 *  *   *   *     /usr/bin/updatedb

Now every five minutes updatedb is run and locate commands database is almost always up-to-date.

But there are no attributes?

You can pipe locate output to other commands. If for example you want the file attributes you can use:

$ locate mail-transport-agent.target | xargs stat
  File: '/lib/systemd/system/mail-transport-agent.target'
  Size: 473         Blocks: 8          IO Block: 4096   regular file
Device: 10305h/66309d   Inode: 667460      Links: 1
Access: (0644/-rw-r--r--)  Uid: (    0/    root)   Gid: (    0/    root)
Access: 2018-03-31 18:11:55.091173104 -0600
Modify: 2017-10-27 04:11:45.000000000 -0600
Change: 2017-10-28 07:18:24.860065653 -0600
 Birth: -

Summary

I posted this answer to show the speed and ease of use of locate. I tried to address some of the command short-comings pointed out by others.

The find command needs to traverse the entire directory structure to find files. The locate command has it's own database which gives it lightning speed in comparison.