GDB is a C debugger for the cli, it allows stepping through a program, setting breakpoints, watching variables and many other more complex things too.

Compiling for GDB

gcc -g program.c -o program 

Use the -g flag to keep the debug symbols in your output binary.

Running GDB

gdb ./program  


Once you launch gdb you will be presented with a basic prompt. Your program wont run untill you type run at the prompt.

Getting a sensible view of your code

At the prompt type d layout src }} to get a view of your code where you can see the debugger progress. Other layouts are available:

next - Display the next layout
prev - Display the previous layout
src - Display the source and command windows
asm - display the assembly and command windows
split - display the src, asm and ccommand windows
regs - display the register window along with src, asm or split.

Setting a breakpoint

{tutorial }

Many ways, here are a few:

break file.c:17 <- set a breakpoint on line 17 in file.c
break func_name <- set a breakpoint at a function start
break (+/-)3 <- set a breakpoint offset from current location

To continure execution after a breakpoint type


at the prompt.


Type an


at the prompt to step to the next line. Type an


to step into a function.

Viewing variables

print variable_name