Function hook_source 

pub fn hook_source() -> String

What: The recording hook’s shell program: write the remote name and location, then the update lines, to a new capture file named by the hook’s process ID. Why: set -C makes the redirection exclusive, so two destinations never overwrite each other’s capture.

In TS you’d write (pseudocode):

hookSource(): string; // `#!${process.execPath}` plus the capture writer