# Basic syntax:
awk '(FNR%4==0) {print length($0)}' your_file.txt > trimmed_file.txt
# Where:
# - FNR is the current file record number (typically the line number)
# - (FNR%4==0) checks whether the current line number is evenly divisible by
# 4, to get the length of every 4th row
# - For line numbers that are evenly divisible by 4, get the length with the
# awk length function