Rowan Smith wrote:

> ps. it is not decending into any directories because no directories have 
> a name that matches *.c. (The star is matched before grep even runs.)

That gave me the thought that I had to wildcard the directory name so I 
tried:

grep -ir foobar ./*/*.c

That appears to have worked!  I must try some of the other solutions for 
my own education.  Thanks to all.

Alan