find command -- sometimes error, sometimes not

markush · 02-05-2014, 04:02 AM

Hi,

when I execute this command

Code:

markus@slackvm:~$ find /home/markus/ -name *.pdf
find: paths must precede expression: find.pdf
Usage: find [-H] [-L] [-P] [-Olevel] [-D help|tree|search|stat|rates|opt|exec] [path...] [expression]

I get an errormessage (obviously). But when I execute it for example as root:

Code:

slackvm:~# find /home/markus/ -name *.pdf
/home/markus/Praes/authent.pdf
/home/markus/signal.pdf
/home/markus/groff_out.pdf
 ....

it works.

Normally I would use -name "*.pdf" when searching with a wildcard, but now I found out that it sometimes works without the "".
I know that it would also work with -name \*.pdf and suppose that the shell will normally expand the *.

Can anyone explain this behaviour? why does it sometimes work and sometimes not. What exactly does the shell do in this cases?

Thanks in advance

Markus

pan64 · 02-05-2014, 04:08 AM

shell tries to understand and evaluate the string *.pdf. If shell could find something, it will be replaced. If not, shell will leave it as it was - and find can use it. Using \ or " will avoid shell evaluation.

markush · 02-05-2014, 04:12 AM

Thanks to pan64, that's the solution.

The shell looks within the directory where the command is executed for *.pdf, since in /root/ there are no pdf-files, it executes the find command as it is. When I change as root to /home/markus/ I get the error because there are pdf files.

Markus