To single step a specified number of lines of code, use the dbx commands next or step followed by the number of lines [n] of code you want executed.
(dbx) next n
or
(dbx) step n
The step_granularity dbxenv variable determines the unit by which the step command and next command step through your code. The unit can be either statement or line.
The step_events environment variable controls whether breakpoints are enabled during a step.
The step_abflow environment variable controls whether dbx stops when it detects that an abnormal control flow change is about to happen. This type of control flow change can be caused by a call to siglongjmp() or longjmp() or an exception throw.
For more information, see Setting dbxenv Variables.