GDB Quick-Reference

This quick-reference table is copyright 2002 Robert M. Dondero, Jr., and is used by permission in this book. Parameters listed in brackets are optional.

Table F-1: Common GDB Debugging Commands

Miscellaneous
quit	Exit GDB
help [cmd]	Print description of debugger command cmd. Without cmd, prints a list of topics.
directory [dir1] [dir2] ...	Add directories dir1, dir2, etc. to the list of directories searched for source files.

Running the Program
run [arg1] [arg2] ...	Run the program with command line arguments arg1, arg2, etc.
set args arg1 [arg2] ...	Set the program's command-line arguments to arg1, arg2, etc.
show args	Print the program's command-line arguments.

Using Breakpoints
info breakpoints	Print a list of all breakpoints and their numbers (breakpoint numbers are used for other breakpoint commands).
break linenum	Set a breakpoint at line number linenum.
break *addr	Set a breakpoint at memory address addr.
break fn	Set a breakpoint at the beginning of function fn.
condition bpnum expr	Break at breakpoint bpnum only if expression expr is non-zero.
command [bpnum] cmd1 [cmd2] ...	Execute commands cmd1, cmd2, etc. whenever breakpoint bpnum (or the current breakpoint) is hit.
Continue	Continue executing the program.
Kill	Stop executing the program.
delete [bpnum1] [bpnum2] ...	Delete breakpoints bpnuml, bpnum2, etc., or all breakpoints if none specified.
clear *addr	Clear the breakpoint at memory address addr.
clear [fn]	Clear the breakpoint at function fn, or the current breakpoint.
clear linenum	Clear the breakpoint at line number linenum.
disable [bpnum1] [bpnum2] ...	Disable breakpoints bpnum1, bpnum2, etc., or all breakpoints if none specified.
enable [bpnum1] [bpnum2] ...	Enable breakpoints bpnum1, bpnum2, etc., or all breakpoints if none specified.

Stepping through the Program
nexti	"Step over" the next instruction (doesn't follow function calls).
stepi	"Step into" the next instruction (follows function calls).
finish	"Step out" of the current function.

Examining Registers and Memory
info registers	Print the contents of all registers.
print/f $reg	Print the contents of register reg using format f. The format can be x (hexadecimal), u (unsigned decimal), o (octal), a(address), c (character), or f (floating point).
x/rsf addr	Print the contents of memory address addr using repeat count r, size s, and format f. Repeat count defaults to 1 if not specified. Size can be b (byte), h (halfword), w (word), or g (double word). Size defaults to word if not specified. Format is the same as for print, with the additions of s (string) and i (instruction).
info display	Shows a numbered list of expressions set up to display automatically at each break.
display/f $reg	At each break, print the contents of register reg using format f.
display/si addr	At each break, print the contents of memory address addr using size s (same options as for the x command).
display/ss addr	At each break, print the string of size s that begins in memory address addr.
undisplay displaynum	Remove displaynum from the display list.

Examining the Call Stack
where	Print the call stack.
backtrace	Print the call stack.
frame	Print the top of the call stack.
up	Move the context toward the bottom of the call stack.
down	Move the context toward the top of the call stack.