Shell Programming and Scripting

As for the second part of your question enoch99:
Try this one:

#!/bin/sh
script content

if you execute this (./scriptname) and it is executable, then it should be executed using #!/bin/sh

you can put the file "script.sh" in /usr/bin .But you will need to have root permissions. you can do that by
sudo mv (or mv -i or cp -i to be safe) script.sh /usr/bin
and then enter your password when prompted.
Any program you have, even a simple c program executable you create can be run by just typing the executable name if it is present in /usr/bin . you can even remove the .sh extension if you want to i guess.I am just an amateur user of UNIX with hardly an year of experience.My apologies for any mistakes.

That's not a good place to put it. That should contain only system-provided commands. The better place is /usr/local/bin, or, if it's just for your own use, $HOME/bin.

It can be run by just typing the executable name if it is present in ANY directory in your $PATH.