Start program:
gdb -tui -args abc 1 2 3
gdb -tui -p <PID>

Debug program:
r = run
c = continue
n = next
s = step
fin = finish
ret abc = return abc
up = up the stack
up 5 = up 5 times
do = down the stack
do 5 = down 5 times

Info program:
p = print
q = quit
bt = backtrace

Breakpoints:
b <location> = break
en 5 = enable breakpoint number 5
dis 5 = disable breakpoint number 5
i b = information on breakpoints

More info: