N5ken's technical blog

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IRB Trick

IRB subsessions let you try things without ending or affecting any of your existing subsessions. The commands to work with subsessions are:

irb start a new subsession
jobs list subsessions
fg # switch to a subsession
kill # kill a subsession

>> my_string = "foo"
=> "foo"
>> irb
>> my_string
NameError: undefined local variable or method `my_string' for main:Object
from (irb#1):1
>> jobs
=> #0->irb on main (#: stop)
#1->irb#1 on main (#: running)
>> fg 0
=> #, @signal_status=:IN_EVAL, @scanner=#>
>> my_string
=> "foo"

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