Inside the archive
Objective
Read a file out of a compressed backup without unpacking it.
The briefing
A backup was taken of a directory and stored as a single compressed file. It sits under a backups directory in your home.
You could unpack the whole thing, but that scatters files everywhere and you only want one of them. The archiving tool can list what is inside without extracting anything, and it can print a single member straight to your terminal.
Two options do that. One lists, one writes to standard output, which is the same thing as printing it.
Set it up
Run this in Termux. It teaches the concept above a second time, then writes the challenge files into your home directory.
ctf start 06 The tool tells you how many files it wrote, never their names.
Then find the flag and hand it in with ctf check 06 LEARMUX{...}.
Hints
Two of them, revealed one at a time. The tool works the same way and remembers how many you have seen, so nothing is spoiled by accident.