Strace Overview
strace can be seen as a light weight debugger. It allows a programmer / user to quickly find out how a program is interacting with the OS. It does this by monitoring system calls and signals.
Uses
Good for when you don’t have source code or don’t want to be bothered to really go through it.
Also, useful for your own code if you don’t feel like opening up GDB, but are just interested in understanding external interaction.
A good little introduction
Here is a gentle introduction to using strace to debug process hangs: strace introduction