strace is a diagnostic, debugging and instructional userspace utility for Linux.

strace is a powerful command line tool for debugging and trouble shooting programs in Unix-like operating systems such as Linux. It captures and records all system calls made by a process and the signals received by the process.
strace is used to monitor and tamper with interactions between processes and the Linux kernel, which include system calls, signal deliveries, and changes of process state. The operation of strace is made possible by the kernel feature known as ptrace. Some Unix-like systems provide other diagnostic tools similar to strace, such as truss.