test for "command not found" before expanding shell parameters

[Toralf Förster]

Under Gentoo Linux I'd like to grep for various things in the package database 
in the following way:

$> greo semanti /var/db/pkg/*/*/USE

This might take a longer time for a low device before I'm faced with the 
message:

"bash: greo: command not found"

/me wonders if it is mandatory first to expand the complete command line before 
realizing that the command isnÄt ther ?

-- 
Toralf