pgrep(1)

pgrep [opts] <pattern>
  -n         only list newest matching process
  -u <usr>   only show matching for user <usr>
  -l         additionally list command
  -a         additionally list command + arguments
  -x         match exactly

Debug newest process

For example attach gdb to newest zsh process from $USER.

gdb -p $(pgrep -n -u $USER zsh)