[bash] Running script upon login mac

Follow this:

• start Automator.app
• select Application
• click Show library in the toolbar (if hidden)
• add Run shell script (from the Actions/Utilities)
• copy & paste your script into the window
• test it

• save somewhere (for example you can make an Applications folder in your HOME, you will get an your_name.app)

• go to System Preferences -> Accounts -> Login items

• add this app
• test & done ;)

EDIT:

I've recently earned a "Good answer" badge for this answer. While my solution is simple and working, the cleanest way to run any program or shell script at login time is described in @trisweb's answer, unless, you want interactivity.

With automator solution you can do things like next:

so, asking to run a script or quit the app, asking passwords, running other automator workflows at login time, conditionally run applications at login time and so on...