All Questions(ubuntu)

I suspect a program is listening on port 8000 on my machine.

When I run the following command, I get this error:

> python -m SimpleHTTPServer
# Lots of python error
socket.error: [Errno 98] Address already in use

If I use another port (8000 is the default), the web server runs fine.

If I run wget localhost:8000 from the command line, it returns 404 Not Found.

What can I do (or what tools are available) to find what program is listening on port 8000, and from there where that program is configured?

How to list all variables names and their current values?

Including not only $HOME, $PWD etc but any other you have defined.

There is a chmod command to set file permissions, but can I get file permissions in octal mode (such as 755) from the command line?

I can issue the clear command or press Ctrl + L to clear the current Ubuntu terminal, but this just shifts previous output upwards and if you use mouse scroll or PgUP and PgDown keys it's hard to distinguish where the output of previous command ends and output of current command begins.

Is there a way to really clear the terminal so I won't see previous command results?

I would like to create an alias to rm command in order to have a confirmation message after executing this command. So I am creating an alias like this alias rm='rm -i'. But as far as I know this is a temporary alias and it lives until you close the terminal.

As it is explained here to save alias permanently I need to execute ~/.bash_aliases or ~/.bashrc commands in terminal and add my alias there. But when I execute ~/.bashrc I get following error message :

bash: /home/bakhtiyor/.bashrc: Permission denied

When I run ~/.bash_aliases I get another error message like this:

bash: /home/bakhtiyor/.bash_aliases: File or directory doesn't exist.

What is the actual problem and how can I solve it?