Print only words with Capital Letters (Linux)

Could you please try following, written and tested with shown samples only in GNU awk.

your_command | awk '
match($0,/"GET \/[a-zA-Z]+\/[^/]*/){
  val=substr($0,RSTART,RLENGTH)
  sub(/.*\//,"",val)
  if(val!~/[a-z]/){  print val  }
  val=""
}'

Single command line:

grep -E '/elv/[A-Z]+' infile | sed -E 's:.*/elv/([A-Z_]+).*:\1:'

if sort is needed/allowed,

 grep -E '/elv/[A-Z]+' infile | sed -E 's:.*/elv/([A-Z_]+).*:\1:' | sort -u

You need to put regex pattern in your awk script to compare $5:

Solution:

grep "/elv" ~/spacestation.txt | awk -F/ '$5 ~ /^[A-Z_]+/ {print $5}' | sort -u 

1. '~' is for compare $5 with regex pattern matching
2. '^' is first character of word
3. '[A-Z_]' will look for all caps-lock characters including with _
4. '+' is for to continue with matching [A-Z_] if he finds one or more character like this