Example GDB commands (from demo 9/11/2013)

These examples use abbreviated command names, because I'm lazy that
way.  GDB has online help with the "help" command, or you can find the
extensive manual on the web (Google "GDB manual").

This list should include all the commands I showed in class, plus a
few extra ones.

Run a program with arguments and also under GDB:
% gdb --args ./eg 5 6 7

Set breakpoint on the first line of a function:
(gdb) b main
(gdb) b func

Start program running:
(gdb) run

Print environment variables:
(gdb) show environment

Print process ID:
(gdb) info proc

Print information about shared libraries:
(gdb) info shared

Print information about threads:
(gdb) info thread

Print stack backtrace:
(gdb) bt

Continue after a breakpoint:
(gdb) c

Disassemble the current function, EIP shown with "=>":
(gdb) disass

Single-step one instruction:
(gdb) stepi

List source code:
(gdb) l

Single-step one instruction, skipping over calls:
(gdb) nexti

Print the program counter (%eip):
(gdb) p $eip

Disassemble the current instruction:
(gdb) x/i $eip

Disassemble a range of instructions:
(gdb) disass 0x0804854f,0x0804855d

Print all integer registers:
(gdb) info reg

Print values of local variables:
(gdb) info locals

Print function arguments:
(gdb) info args

Print information about current stack frame:
(gdb) info frame

Print the value at a memory location, C style:
(gdb) p *(void **)(0xffffd49c)

Print the value at a memory location, with "x":
(gdb) x/xw 0xffffd49c

Print the value at 4(%ebp), C style:
(gdb) p *(void **)($ebp + 4)

Print the address of a local variable, C style:
(gdb) p &buf

Print the distance between two stack locations, C style:
(gdb) p (void *)($ebp + 4) - (void *)&buf

Set a breakpoint at an instruction:
(gdb) b *0x0804857d

Print the type of a variable:
(gdb) ptype buf

Print the definition of a type (when debug info available):
(gdb) ptype struct stat

Break on changes to a memory location:
(gdb) watch *(void **)0xffffd49c