#!/bin/bash
cd $(mktemp -d)
echo ">day_1
ABC
DEF
GHI
>day_2
JKL
MNO
PQR
>day_3
STU
VWX
YZA
>month_1
BCD
EFG
HIJ
>month_2
KLM
NOP
QRS" > input.txt
lines_by_subcategory=3 # number of lines *after* a subcategory's header
for category in 'month' 'day'; do
grep ">$category" -A $lines_by_subcategory input.txt >> "$category.txt"
done
echo "directory content :"
ls
echo "month.txt :"
cat month.txt
echo "day.txt :"
cat day.txt
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