GDB Cheat Sheet

Running

`# gdb <program> [core dump]`	Start GDB (with optional core dump)
`# gdb --args <program> <args...>`	Start GDB and pass arguments
`# gdb --pid <pid>`	Start GDB and attach to process
`set args <args...>`	Set arguments to pass to program to be debugged
`run`	Run the program to be debugged
`kill`	Kill the running program

Breakpoints

`break <where>`	Set a new breakpoint
`delete <breakpoint#>`	Remove a breakpoint
`clear`	Delete all breakpoints
`enable <breakpoint#>`	Enable a disabled breakpoint
`disable <breakpoint#>`	Disable a breakpoint

Watchpoints

`watch <where>`	Set a new watchpoint
`delete <watchpoint#>`	Delete a watchpoint
`enable <watchpoint#>`	Enable a disabled watchpoint
`disable <watchpoint#>`	Disable a watchpoint

Where

`function_name`	Break/watch the named function
`line_number`	Break/watch the line number in the current source file
`file:line_number`	Break/watch the line number in the named source file

Conditions

`break/watch <where> if <condition>`	Break/watch at the given location if the condition is met. Condition may be almost any C expression that evaluates to `true` or `false`
`condition <breakpoint#> <condition>`	Set/change the condition of an existing break or watchpoint

Examining the Stack

backtrace

where

Show call stack

backtrace full

where full

Show call stack, also print the local variables in each frame

frame <frame#>

Select the stack frame to operate on

Stepping

`step`	Go to next instruction (source line), diving into function
`next`	Go to next instruction (source line) but do not dive into function
`finish`	Continue until the current function returns
`continue`	Continue normal execution

Variables and Memory

`print/format <what>`	Print content of variable/memory location/register
`display/format <what>`	Like `print`, but print the information after each stepping instruction
`undisplay <display#>`	Remove the `display` with the given number
`enable display <display#>` `disable display <display#>`	Enable or disable the `display` with the given number
`x/nfu <address>`	Print memory `n`: How many units to print (default 1) `f`: Format character (like `printf`) `u`: Unit Unit is one of: `b` (Byte), `h` (Half-word/two bytes), `w` (Word/four bytes), `g` (Giant-word/eight bytes)

Format

`a`	Pointer
`c`	Read as integer, print as character
`d`	Integer, signed decimal
`f`	Floating point number
`o`	Integer, print as octal
`s`	Try to treat as C string
`t`	Integer, print as binary (t = 'two')
`u`	Integer, unsigned decimal
`x`	Integer, print as hexadecimal

What

`expression`	Almost any C expression, including function calls (must be prefixed with a cast to tell GDB the return value type)
`file_name::variable_name`	Content of the variable defined in the name file (static variables)
`function_name::variable_name`	Content of the variable defined in the name function (if on the stack)
`{type}address`	Content at address, interpreted as being of the C type `type`
`$register`	Content of named register. Interesting registers are `$esp` (stack pointer), `$ebp` (frame pointer) and `$eip` (instruction pointer)

Threads

thread <thread#>

Choose thread to operate on

Manipulate the Program

`set var <variable_name>=<value>`	Change the content of a variable to the given value
`return <expression>`	Force the current function to return immediately, passing the given value

Sources

directory <directory>

Add directory to the list of directories that is searched for sources

list

list <filename>:<function>

list <filename>:<line_number>

list <first>, <last>

Shows the current or given source context. The filename may be omitted. If last is omitted the context starting at start is printed instead of centered around it

set listsize <count>

Set how many lines to show in list

Signals

handle <signal> <options>

Set how to handle signals

Options are:
(no)print: (Do not) print a message when signals occur
(no)stop: (Do not) stop the program when signals occur
(no)pass: (Do not) pass the signal to the program

Information

`disassemble` `disassemble <where>`	Disassemble the current function or given location
`info args`	Print the arguments to the function of the current stack frame
`info breakpoints`	Print information about the breakpoints and watchpoints
`info display`	Print information about the `display`
`info locals`	Print the local variables in the currently selected stack frame
`info sharedlibrary`	List loaded shared libraries
`info signals`	List all signals and how they are currently handled
`info threads`	List all threads
`show directories`	Print all directories in which GDB searches for source files
`show listsize`	Print how many are shown in the `list` command
`whatis variable_name`	Print type of named variable

GDB

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