truss is a system tool available on some Unix-like operating systems. When invoked with an additional executable command-line argument, truss makes it possible to print out the system calls made by and the signals received by this executable command-line argument. As of version IEEE Std 1003.1-2008, truss is not part of the Single UNIX Specification (POSIX).

The truss command was originally developed by Roger Faulkner and Ron Gomes as part of the development of Procfs for System V Release 4. While several names were considered, “truss” was chosen for being non-ambiguous and easily pronounceable, with multiple meanings, including as an abbreviation for TRace Unix Syscalls and Signals or in the sense of “If your program doesn’t work, put it in a truss.”^[1]