Q:

Run executable file on terminal

I'm new to Ubuntu and currently on it because of assignment. I would like to ask few questions:

How do I make new command to run a shell script?
For example, when you type passwd on terminal it runs the executable file on    /usr/bin/passwd. 
How do I make it the same like my file?
How do I change my shell script into a executable file like the passwd?

A:

Your script should look like:
#!/bin/bash

passwd

Save it in a file, let say password.sh or simple password, then make it executable using next commands in terminal:
cd /path/to/password.sh  #or cd /path/to/password
chmod +x password.sh     #or chmod +x password

To run it from terminal, just use the following command:
./password.sh            #or ./password

or
/path/to/password.sh     #or /path/to/password

To run it only using:
password.sh              #or password

you must to add the path of the script to the PATH. See How to add a directory to the PATH? in this sense.

