How can I open a text file with TextWrangler from the Terminal (command line)?
As a one-time thing,

open -a /Applications/TextWrangler.app myfile.txt
open -b com.barebones.textwrangler myfile.txt # same thing by ID


You can also create an alias for opening TextWrangler, that you would put on the .bash_profile file, which is an hidden file by default that is usually in your home directory. 

This is the command that you could insert:

# Type 'tw' on the terminal to open TextWrangler
alias tw='open -a /Applications/TextWrangler.app'


To make TextWrangler the default:


"Get Info" on a text file in the Finder.
Change the "Open with:" program to TextWrangler, in the fifth information pane.
Click the "Change All..." button at the bottom of the pane.