Gdbcomm

Startup 
% gdb -help             print startup help, show switches
*% gdb object       normal debug 
*% gdb object core  core debug (must specify core file)
%% gdb object pid   attach to running process
% gdb               use file command to load object 

Help
*(gdb) help         list command classes
(gdb) help running      list commands in one command class
(gdb) help run          bottom-level help for a command "run" 
(gdb) help info         list info commands (running program state)
(gdb) help info line    help for a particular info command
(gdb) help show         list show commands (gdb state)
(gdb) help show commands        specific help for a show command

Breakpoints
*(gdb) break main       set a breakpoint on a function
*(gdb) break 101        set a breakpoint on a line number
*(gdb) break basic.c:101        set breakpoint at file and line (or function)
*(gdb) info breakpoints        show breakpoints
*(gdb) delete 1         delete a breakpoint by number
(gdb) delete            delete all breakpoints (prompted)
(gdb) clear             delete breakpoints at current line
(gdb) clear function    delete breakpoints at function
(gdb) clear line        delete breakpoints at line
(gdb) disable 2         turn a breakpoint off, but don't remove it
(gdb) enable 2          turn disabled breakpoint back on
(gdb) tbreak function|line        set a temporary breakpoint
(gdb) commands break-no ... end   set gdb commands with breakpoint
(gdb) ignore break-no count       ignore bpt N-1 times before activation
(gdb) condition break-no expression         break only if condition is true
(gdb) condition 2 i == 20         example: break on breakpoint 2 if i equals 20
(gdb) watch expression        set software watchpoint on variable
(gdb) info watchpoints        show current watchpoints

Running the program
*(gdb) run          run the program with current arguments
*(gdb) run args redirection        run with args and redirection
(gdb) set args args...        set arguments for run 
(gdb) show args        show current arguments to run
*(gdb) cont            continue the program
*(gdb) step            single step the program; step into functions
(gdb) step count       singlestep \fIcount\fR times
*(gdb) next            step but step over functions 
(gdb) next count       next \fIcount\fR times
*(gdb) CTRL-C          actually SIGINT, stop execution of current program 
*(gdb) attach process-id        attach to running program
*(gdb) detach        detach from running program
*(gdb) finish        finish current function's execution
(gdb) kill           kill current executing program 

Stack backtrace
*(gdb) bt           print stack backtrace
(gdb) frame         show current execution position
(gdb) up            move up stack trace  (towards main)
(gdb) down          move down stack trace (away from main)
*(gdb) info locals      print automatic variables in frame
(gdb) info args         print function parameters 

Browsing source
*(gdb) list 101         list 10 lines around line 101
*(gdb) list 1,10        list lines 1 to 10
*(gdb) list main    list lines around function 
*(gdb) list basic.c:main        list from another file basic.c
*(gdb) list -           list previous 10 lines
(gdb) list *0x22e4      list source at address
(gdb) cd dir            change current directory to \fIdir\fR
(gdb) pwd           print working directory
(gdb) search regexpr    forward current for regular expression
(gdb) reverse-search regexpr        backward search for regular expression
(gdb) dir dirname       add directory to source path
(gdb) dir           reset source path to nothing
(gdb) show directories        show source path

Browsing Data
*(gdb) print expression        print expression, added to value history
*(gdb) print/x expressionR        print in hex
(gdb) print array[i]@count        artificial array - print array range
(gdb) print $           print last value
(gdb) print *$->next    print thru list
(gdb) print $1          print value 1 from value history
(gdb) print ::gx        force scope to be global
(gdb) print 'basic.c'::gx        global scope in named file (>=4.6)
(gdb) print/x &main     print address of function
(gdb) x/countFormatSize address        low-level examine command
(gdb) x/x &gx           print gx in hex
(gdb) x/4wx &main       print 4 longs at start of \fImain\fR in hex
(gdb) x/gf &gd1         print double
(gdb) help x            show formats for x
*(gdb) info locals      print local automatics only
(gdb) info functions regexp         print function names
(gdb) info variables  regexp        print global variable names
*(gdb) ptype name        print type definition
(gdb) whatis expression       print type of expression
*(gdb) set variable = expression        assign value
(gdb) display expression        display expression result at stop
(gdb) undisplay        delete displays
(gdb) info display     show displays
(gdb) show values      print value history (>= gdb 4.0)
(gdb) info history     print value history (gdb 3.5)

Object File manipulation
(gdb) file object           load new file for debug (sym+exec)
(gdb) file                  discard sym+exec file info
(gdb) symbol-file object        load only symbol table
(gdb) exec-file object      specify object to run (not sym-file)
(gdb) core-file core        post-mortem debugging

Signal Control
(gdb) info signals          print signal setup
(gdb) handle signo actions      set debugger actions for signal
(gdb) handle INT print          print message when signal occurs
(gdb) handle INT noprint        don't print message
(gdb) handle INT stop           stop program when signal occurs
(gdb) handle INT nostop         don't stop program
(gdb) handle INT pass           allow program to receive signal
(gdb) handle INT nopass         debugger catches signal; program doesn't
(gdb) signal signo          continue and send signal to program
(gdb) signal 0              continue and send no signal to program

Machine-level Debug
(gdb) info registers            print registers sans floats
(gdb) info all-registers        print all registers
(gdb) print/x $pc           print one register
(gdb) stepi             single step at machine level
(gdb) si                single step at machine level
(gdb) nexti             single step (over functions) at machine level
(gdb) ni                single step (over functions) at machine level
(gdb) display/i $pc         print current instruction in display
(gdb) x/x &gx               print variable gx in hex
(gdb) info line 22          print addresses for object code for line 22
(gdb) info line *0x2c4e         print line number of object code at address
(gdb) x/10i main            disassemble first 10 instructions in \fImain\fR
(gdb) disassemble addr          dissassemble code for function around addr

History Display
(gdb) show commands         print command history (>= gdb 4.0)
(gdb) info editing          print command history (gdb 3.5)
(gdb) ESC-CTRL-J            switch to vi edit mode from emacs edit mode
(gdb) set history expansion on       turn on c-shell like history
(gdb) break class::member       set breakpoint on class member. may get menu
(gdb) list class::member        list member in class
(gdb) ptype class               print class members
(gdb) print *this           print contents of this pointer
(gdb) rbreak regexpr        useful for breakpoint on overloaded member name

Miscellaneous
(gdb) define command ... end        define user command
*(gdb) RETURN               repeat last command
*(gdb) shell command args       execute shell command 
*(gdb) source file          load gdb commands from file
*(gdb) quit             quit gdb