breakpoint not reached by in cli

[wong_powah]

I had written a command line interface program cli.c.
# useradd -m -G users,wheel -s /home/powah/cli/cli operator
# su - operator
#ps -ef |grep cli

Attach gdb to the cli process id:
#gdb -p <pid>

Set a breakpoint:
(gdb) b func
(gdb) cont

When the cli function is executed, the func breakpoint is not reached.
cli>users list

I am sure I have set the breakpoint at the right function, so what is
wrong?