Displaying stuff:

print displays the value in
x displays the value pointed at by
display displays after each command
undisplay removes display #
Any of these commands can have a format argument appended:

/d decimal
/u unsigned
/x hex
/t binary
/i instruction
/s string (displays ascii values until a nul is encountered)
/c char

display /i $eip is a useful command. It displays the value pointed at by $eip after each command and interprets it as an instruction. Basically it shows the next instruction to be run.
Also, if a size and number are given, it will print that many of those size items after the given thing.
I.E. x/20w $esp displays 20 words at and after $esp.
sizes are:
/b byte
/w word

Breakpoints:

break (some function) or
break (line number) or
break *(some memory address) or
delete (breakpoint number)

clear (some functionr) or
(some line number) or
*(some memory address)

Running:

stepi steps one instruction, going into function calls
nexti steps one instruction, not going into function calls
run restarts the program at full speed
continue goes at full speed after a breakpoint
kill end the program running

Command Line:

set args (stuff) passes as command line arguments to the program
file loads as the program to be run

Lazy Typing:

enter at an empty command line repeats the last command ambigious abreviations will resolve to the last command with that abbreviation

Lazy Math:

print/d 0x(some hex number) will convert it to decimal
print/h (some decimal number) will convert it to hex More complicated expressions will probably work too.

This is my short list of useful commands

• make – run make. It can take arguments just like on the command line.
• enter – do the same command again.
• n (next) – move to the next source line in the file.
• s (step) – step into the function.
• finish – step out of the current function.
• break filename:line number – set a breakpoint at a particular line.
• clear – clear the breakpoint you are stopped on.
• bt (backtrace) – show the current stack.
• frame n – go to the nth stack frame.
• info threads – list the current threads.
• thread n – look at the nth thread.
• print something – print a variable's value, or evaluate something (such as print sizeof(foo)
• info locals – print all local variables.
• info args – print all of the arguments to the current function as they are now (as opposed to as they were at the top of the function).
• call function – call a function.
• whatis something – print the type of a thing.
• x – just look at help x. This does memory dumps in many formats.

Mike Erlinger