UNIX for Dummies Questions & Answers

Hi all,
Today I was just fooling around with directories and faced this. I create a directory 'testdir' and create a file 'myfile' inside it.

Code:

gandalf@gondor:~$ mkdir testdir
gandalf@gondor:~$ cd testdir
gandalf@gondor:~/testdir$ touch myfile

Then I set the following permissions for the directory.

Code:

gandalf@gondor:~$ chmod 664 testdir

The file inside the directory has 644 permissions.

Code:

gandalf@gondor:~/testdir$ ls -l
total 0
-rw-r--r-- 1 gandalf gandalf 0 2007-08-10 22:17 myfile

Now. I can 'cd' to the directory. I can do a 'ls' on that directory.

Code:

gandalf@gondor:~$ ls testdir
testdir/myfile

Now, if I try a 'cat' on the file, it fails.

Code:

gandalf@gondor:~$ cat testdir/myfile
cat: testdir/myfile: Permission denied

The file has read permissions and the directory too has read permissions. Then why is cat not able to read and display the file? Is it dependent on the implementation of 'cat'? My box is

Code:

gandalf@gondor:~/testdir$ uname -a
Linux gondor 2.6.15-28-386 #1 PREEMPT Wed Jul 18 22:50:32 UTC 2007 i686 GNU/Linux

You don't have execute permissions on the directory which let you use it as part of a path.

Thanks for the reply. But does 'cat' move to the directory and then read the file. I was assuming that since 'read' permissions were available for the directory and the file, 'cat' should be able to print it put. How does 'cat' really work then?

It's nothing to do with cat.

If I do "cat file" then all I need is to read the file.

If I do "cat dir/file" then I need to first navigate through dir to get to file.

The execute permission on a directory allows this navigation.

Ok! got that Porter. Thanks again!!

Check whether the file is readable or not using vi command

vi <filename.extension>

Some time we can't open the file where file insdie the not executable permission dir.


Regards,
Siva.P
Bangalore

If you are craeting a file inside a directory then the first thing you have to consider is the permissions of the directory,if the dir has sufficient permissions then only you an can do manipulations on the file.
Its something like this--

You are standing infront of a house,inside the house you ahve so many treasures,but you do not have the door key.

Thanks,
Namish