Using the Return Value

Functions, like programs, succeed or fail. That's what $? is about. (At the shell level, $? tells whether the last command succeeded or failed. Here, as far as the shell is concerned, the function is just like a command.)

This means that if you have a function to check out and build code

get-N-make() {
 svn co $*
 (
  cd $_
  make
 )
} &> /dev/null

You can call it like this:

get-N-make -Dyesterday mycode ||
 die "something in the checkout or build failed"

(Notice that you can redirect the output of a function as part of its definition.