I mean, is there a way to make the command `chmod'
act upon files in a certain directory that have not been created yet?
For example:

# mkdir mydir
# touch mydir/file1
# ls -l mydir
total 0
-rw-r--r-- 1 root root 0 ago 16 12:36 file1
# chmod go-r mydir/*
# ls -l mydir
total 0
-rw------- 1 root root 0 ago 16 12:36 file1
# touch mydir/file2
# ls -l mydir
total 0
-rw------- 1 root root 0 ago 16 12:36 file1
-rw-r--r-- 1 root root 0 ago 16 12:38 file2

. The new file created, file2, is not affected by the command '# chmod go-r mydir/*'
previously given. Was it possible, and how,
that file2 were born with same permissions of file1?

Thanks for any reply,
Rodolfo

UMASK affects the permissions that a file/directory gets when it is created.
If i understand correctly, this is what you mean.
the parameter it gets is the octal number that gets subtracted from 666 (rw-) or 777 (rwx for directories)
In your example you want rw for owner and nothing for others so you want permissions 600, so the umask is 077
usual examples of umask is 077 (which gives rw-------) and 022 (which givers rw-r--r--)
As you see you have 022 umask that is why the file2 gets those permissions.

I don't know what distribution you use, but usually every major distribution uses a default umask in /etc/profile for /bin/bash

For example my /etc/profile has the following:

# Default umask. A umask of 022 prevents new files from being created group
# and world writable.
umask 022

Thanks:
but umask does not allow to select a desired file,
it affects all new files of all directories, doesn't it?
I was meaning a way to change permissions for
future new files of a desired directory.
Insn't this possible?

Cheers,
Rodolfo

I would think that any new file would default to the permissions of the directory---and perhaps to the user who created it.

I don't think you can pre-ordain anything but the default behavior---and I don't know why you would want to. One of the worst things with computers is some non-standard behavior caused by **someone** (including you) setting a preference and then forgetting what was set.

All right, thank you.

Rodolfo