unset command for bash

unset

Remove variable or function names

Syntax
      unset [-fv] [name]

Options
      -f    The names refer to shell Functions, 
            and the function definition is removed.
            Readonly variables and functions may not be unset. 

      -v    Each name refers to a shell Variable (default)

The return status is zero unless a name does not exist or is readonly.

unset is a bash built in command.

example:

$ MYDEF=3939   #env command will not output MYDEF

$ echo $MYDEF

3939

$ export MYDEF

$ env |grep 'MYDEF'
MYDEF=3939
$ unset MYDEF     #remove the MYDEF environment variable
$ env |grep 'MYDEF'

"A good trader has to have three things: a chronic inability to accept things at face value, to feel continuously unsettled, and to have humility" - Michael Steinhardt