gistfile1.sh

~% echo "" > bar 
~% cat bar

~% irb
1.9.3-p547 :001 > f = File.open("bar", "w")
 => #<File:bar> 
1.9.3-p547 :002 > f.write("test1")
 => 5 
1.9.3-p547 :003 > 
zsh: suspended  irb
~% irb
1.9.3-p547 :001 > f = File.open("bar", "w")
 => #<File:bar> 
1.9.3-p547 :002 > f.write("test2")
 => 5 
1.9.3-p547 :003 > f.close
 => nil 
1.9.3-p547 :004 > 
~% cat bar
test2%                                                                                                                                ~% fg
[1]  + continued  irb
1.9.3-p547 :004 > f.close
 => nil 
1.9.3-p547 :005 > 
~% cat bar
test1%