OllyDbg: Automatically extract string when breakpoint is hit

Question

Given a breakpoint at an expression MOV EDI, EAX, how can you automatically log/write to file the referenced string whenever the breakpoint is hit?

Answer 1

Select the MOV EDI, EAX instruction and press Shift+F4 to open the Conditional log breakpoint window.

In that window, specify eax as the expression, set Pause program to Never, and set Log value of expressions to Always:

Press the OK button, run your program, and now the referenced string will get logged to OllyDbg's log window whenever that instruction is hit.

Answer 2

in odbg version 1.10 that will only log eax not the string
in the expression box put either STRING [EAX] or UNICODE [eax] as the case may be
or with plain eax select pointer to ascii or unicode string in decode expression as dropdown box to log strings

Log data, item 0 Message=eax = 1001590 [eax] = 74636868 string [eax] = hhctrl.ocx unicode [eax] =

odbg 210 will decode expression automatically

01012475  INT3: plain eax = 1001590 ASCII "hhctrl.ocx"
                dword ptr eax = 74636868 (1952671848.)
                ascii string ptr eax = hhctrl.ocx