Piping to the command substitution of a string containing pipes

When you want to run variables that contain code you'll often want to use the command eval. This will expand the contents of the variable so that they can be executed.

Example

$ x='grep a | grep b'
$  echo ab | eval "$x"
ab

Using eval is often discourage though, so use caution, see this BashFAQ titled: Eval command and security issues for more examples!

References

• Execution of a command in a variable with eval

Ah, I figured it out after some experimentation—use alias—

$ x='grep a | grep b'
$ alias y=$x
$ echo ab | y
ab

Please do post any other ways to do this—I'd be interested in alternatives.