The truss utility traces the system calls, signals, and machine faults of a process. It has been enhanced with a new option to enable entry and exit tracing of user-level function calls executed by the traced process. Optional shell-like patterns specify the functions and the library to be traced.
Other truss enhancements include optional time stamps and the ability to leave the traced process stopped and abandoned on selected events. A debugger or other process inspection tool can then be applied to the stopped process.
For more information, see the man page truss(1).