strange behavior of find

tkmsr · 05-12-2010, 06:04 AM

Today while working with some file I had to search all files or directories that were beginning with red5
I was at that time in /usr/lib directory and issued

Code:

server:/usr/lib# find / -name red5*

and got following output.

Code:

/etc/init.d/red5-server
/etc/default/red5-server
/etc/red5
/etc/red5/red5.xml
/etc/red5/red5.policy
/etc/red5/red5-core.xml
/etc/red5/red5-common.xml
/etc/red5/red5.properties
/etc/red5/red5.globals
/usr/share/red5
/usr/share/red5/red5.jar
/usr/share/red5/red5-remoting.jar
/root/red5-server_0.9~svn3968-2_all.deb
/var/log/red5
/var/log/red5/red5.log
/var/run/red5-server.pid
/var/cache/apt/archives/red5-server_0.9~svn3968-2_all.deb
/var/lib/dpkg/info/red5-server.postrm
/var/lib/dpkg/info/red5-server.list

After some time
from /usr/share I executed

Code:

find / -name red5*

and the output had changed

Code:

/etc/red5
/usr/share/red5
/var/log/red5

I had not deleted any file in this duration.

I again excuted from my home directory.

Code:

find / -name red5*

The out put this time was even strange.

Code:

/root/red5-server_0.9~svn3968-2_all.deb
/var/cache/apt/archives/red5-server_0.9~svn3968-2_all.deb

Can some one let me know why is this happening?

I am using
2.6.26-2-xen-amd64

AlucardZero · 05-12-2010, 06:51 AM

Easy, your shell is expanding your wildcard. Quote it so that find gets it instead. "red5*"

tkmsr · 05-12-2010, 06:55 AM

Yes even I wanted the shell to expand the wild card.But why are the results different when they are issued from different directories.In each case I am gave it to search from /

catkin · 05-12-2010, 07:08 AM

It happened because when you issued the command in a directory with no files-or-directories matching red5* the shell was unable to expand it so left it as red5* and find looked under / for files matching red5*.

When you issued the command in a directory with files-or-directories matching red5* (let's assume you were in the /etc directory) the shell expanded it to red5 and find looked under / for files called exactly red5.

You can see what is happening by running echo red5* when /etc is your current diretory and when another directory without any red* files-or-directories like this

Code:

c@CW8:~$ cd /tmp
c@CW8:/tmp$ echo red*
red*
c@CW8:/tmp$ touch red5
c@CW8:/tmp$ echo red*
red5

tkmsr · 05-12-2010, 07:21 AM

Quote:

Originally Posted by catkin

When you issued the command in a directory with files-or-directories matching red5* (let's assume you were in the /etc directory) the shell expanded it to red5 and find looked under / for files called exactly red5.

You can see what is happening by running echo red5* when /etc is your current diretory and when another directory without any red* files-or-directories like this

Code:

c@CW8:~$ cd /tmp
c@CW8:/tmp$ echo red*
red*
c@CW8:/tmp$ touch red5
c@CW8:/tmp$ echo red*
red5

If some one reads man page of find in examples it is given
find /tmp -name core
meaning if you have to find a file core
in directory /tmp you will execute it the above way.
it no where says find will stop searching if it finds the files in current directory.find need to search sub directories in /tmp as well.
Had it been the case it would not have given me results from other directories.

catkin · 05-12-2010, 07:44 AM

Quote:

Originally Posted by tkmsr

it no where says find will stop searching if it finds the files in current directory.find need to search sub directories in /tmp as well.

Correct but not relevant to what is happening here.

The key concept here is what is passed to the find executable. Depending on which directory you are in, entering the command find / -name red5* at the command prompt results in a actual find command of find / -name red5* or find / -name red5

tkmsr · 05-12-2010, 08:24 AM

Quote:

Originally Posted by catkin

find / -name red5* at the command prompt results in a actual find command of find / -name red5* or find / -name red5

Exactly this is what I am also saying.But output changed when I issued from different directories.What had directories to do
when I had already passed /
to start search from /

The output should be same which ever directory I issue.
Unless I say some thing like

Code:

find . -name red5*

johnsfine · 05-12-2010, 08:30 AM

The important fact the OP seems to be ignoring is that the shell interprets red5* before passing it to whatever command (find in this case) was specified.

If there are any files in the shell's current directory matching red5*, then the shell will replace the red5* in the command line with the list of such files.

Quote:

Originally Posted by tkmsr

If some one reads man page of find

The man page for each individual command is not supposed to remind you of behaviors of the shell. It tells you what find does with the command that the shell passes to find.

Quote:

Originally Posted by tkmsr

What had directories to do
when I had already passed /
to start search from /

That / tells find where to search. It does not mean anything to the shell, especially not to the shell's processing of red5*.

As you were already told earlier in this thread, if you want find to get the red5* without the shell processing it first, use "red5*"

catkin · 05-12-2010, 08:31 AM

Quote:

Originally Posted by tkmsr

Exactly this is what I am also saying.But output changed when I issued from different directories.What had directories to do
when I had already passed /
to start search from /

The output should be same which ever directory I issue.
Unless I say some thing like

Code:

find . -name red5*

No because if there is a file-or-directory matching red5* in the directory you are in, the shell itself will expand red5* to its name. In your case there was a file called red5 so find never saw red5*, it only saw red5 and did what it was told to do -- it looked everywhere under / for red5 and reported what it found. Try these commands which will illustrate the how the shell does filename expansion

Code:

mkdir /tmp/my_tmp
cd /tmp/my_tmp
echo red*
touch red5
echo red*