strace is a useful diagnositic, instructional, and debugging tool. System adminstrators, diagnosticians and troubleshooters will find it invaluable for solving problems with programs for which the source is not readily.

strace is a system call tracer, i.e. a debugging tool which prints out a trace of all the system calls made by a another process/program.

Linux to monitor the system calls used by a program and all the signals it receives.