strace

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

Usage and features

The most common use is to start a program using strace, which prints a list of system calls made by the program. This is useful if the program continually crashes, or does not behave as expected; for example using strace may reveal that the program is attempting to access a file which does not exist or cannot be read.

Examples

strace can be used to follow a program directly or using the PID as seen below.

   strace ls

   strace -p $(PID)