There is a lot of output here, but you can grep around or filter with strace CLI. If you used -f option you should get PID numbers later on. Then you can look for all execve's to see how PIDs map to parts of the pipeline. For now maybe grep the log file with something like: "grep -e clone -e execve -e write -e read". You can do this with strace CLI, but I never remember the syntax and usually analyze the log extensively.

I think something like this could work:

  strace -f -e execve,clone,write,read -o strace.log sh -c '...'

Clone is fork, so a creation of a new process, before eventual execve (with echo there will probably be just clone).