File Descriptor 63

kshkid · 03-01-2006, 08:58 AM

Hi All,

When going through the VFS /proc in Solaris,

i noticed the following files for each of the login which spawned a shell($$)

/proc/$$/fd/ - dir

i could notice the file /proc/$$/fd/63 which acts as a exact replica of the .sh_history in $HOME directory.

Why two files are maintained?

Though with enough permissions i couldnt change the permissions set for the file-63.

Has the above file got any other significance in VFS.

Thanks

jlliagre · 03-01-2006, 09:55 AM

Quote:

Originally Posted by kshkid

Hi All,

When going through the VFS /proc in Solaris,

i noticed the following files for each of the login which spawned a shell($$)

/proc/$$/fd/ - dir

i could notice the file /proc/$$/fd/63 which acts as a exact replica of the .sh_history in $HOME directory.

Why two files are maintained?

There aren't two files but a single one.

/proc/$$/fd/63 is representing file descriptor 63 which happens to be .sh_history, as the korn shell keep this file open.

"man -s 4 proc" for details

kshkid · 03-02-2006, 12:49 AM

That was gr8, amazing.

One more to go with as an addition.

So the .sh_history file as that many file descriptors pointing to it .. as that many logins are invoked from the same user with common HOME directory.

the file-63 is under the control of the user, but we are unable to change the permissions of the file.
Why is that so?

jlliagre · 03-02-2006, 11:41 AM

Yes, the history file is, by default, shared between every sessions open by the same user. This is a korn shell feature, and it's often convenient to be able to replay a command picked from the history coming from a different window than the one which first fire it.

Why do you want to change this file's permissions ?

If you really want to, which you shouldn't, do it on the user home directory, the /proc is not there to allow you doing that so chmod isn't implemented for the proc filesystem.