Due to System Integrity Protection (SIP) in macOS, you must enable DTrace by booting into recovery mode (cmd+r), starting terminal, and either disabling SIP altogether by running csrutil disable or alternatively using experimental option csrutil enable --without dtrace (after you have first disabled SIP).
Snoop what is written in specific bash process
You can use echo $$ for shell pid to find your bash window pid
Script usage: sudo ./pidlogger.d -p <pid>
Monitor TCP SEND and RECEIVE commands
Script usage: sudo ./tcpsnoop.d
Simple example of tracing c code (trivial.c)
Usage: sudo dtrace -s ./tracetrivial.d -p <pid>
Trace file open calls per process exec
Script usage: sudo ./openings.d