gdb quickie

gcc -g to compile a program and include debugging information
start - begin exexuting your program

list - examine your source code from within the debugger

step - execute the next line of your program
next - execute the next line of your program, but if it's a subroutine call, treat the entire subroutine as a single line

print - examine the contents of a variable
x - examine memory directly

watch, rwatch - set a watch for when a variable is written or read: return to the debugger once this happens
break - set a breakpoint: return to the debugger when this line of code is about to be executed
info watch - show info on watchpoints
info break - show info on breakpoints
delete # - delete watchpoint or breakpoint "#"

cont - continue from a breakpoint, watchpoint, step, next, etc.; basically begin running your program from where it left off

set var name=value set the value of variable "name" to "value"

bt - show the call frames for your program
frame # - set the current frame to #. Variables you reference etc. will be those within that context.

quit - leave the debugger