Get under surveillance script

#!/bin/ksh
#
# Quick-and-dirty Script to fetch the KXCI radio show Under Surveillance from 
# last Friday (available that Saturday).
#
# Works in ksh, bash, and probably others.
#
# Dependencies: awk, pv, figlet, wget, ffmpeg, mid3v2
#
# by david, david@sidiprojects.us (0x5AFF330ADEFD0AE2C59E9C3DD7362C75283B6B3D)
# 12 Jan 2022
# Licensed under WTFPL


function do_exit_tasks {
   rm "${SAVEDIR}/${ORIGINAL_MANIFEST_NAME}" 2>/dev/null
   rm "${SAVEDIR}/${NEW_MANIFEST_NAME}" 2>/dev/null
}
trap do_exit_tasks EXIT


function do_interrupt_tasks {
   read answer?"Erase the directory for this week's Under Surveillance (${SAVEDIR}) [y/N]?"
   [[ "${answer}" = "y" ]] && rm -rf "${SAVEDIR}"
}
trap do_interrupt_tasks SIGINT


function write_line {
   TERMINAL_WIDTH=$(stty size | cut -d' ' -f2)
   for ((j=0; j<$TERMINAL_WIDTH; j++)); do
      echo -n "-" >&2
   done
   echo >&2
}


function display_banner {
   write_line; write_line
   echo Getting >&2
   figlet -t "UNDER SURVEILLANCE" >&2
   echo for $(date -d "${DATE_TO_GET}" +%F) >&2
   write_line; write_line
}


# MAIN FUNCTION
[[ $(date +%A) = "Saturday" ]] && DATE_TO_GET="now" || DATE_TO_GET="last saturday"
YEAR=$(date -d "${DATE_TO_GET}" +%Y)      # full year (e.g., 2015)
MONTHNAME=$(date -d "${DATE_TO_GET}" +%b) # month abbrev. name (e.g., Oct)
MONTH=$(date -d "${DATE_TO_GET}" +%m)     # month number (e.g., 10)
DAY=$(date -d "${DATE_TO_GET}" +%d)       # day, with 2 digits (e.g., 31)
SAVEDIR="${HOME}/Music/under_surveillance/${MONTHNAME}_${DAY}_${YEAR}"
ORIGINAL_MANIFEST_NAME="index.m3u8"
NEW_MANIFEST_NAME="newindex.m3u8"
SHOW_LENGTH=736

if mkdir ${SAVEDIR} 2> /dev/null; then
   cd $SAVEDIR
   display_banner
else
   echo "Directory $SAVEDIR already exists. Exiting..." >&2
   exit 1 
fi

remote_dirname="KXCI-${YEAR}${MONTH}${DAY}T050000Z"
local_filename="Under-Surveillance_${DAY}-${MONTHNAME}-${YEAR}.mp3"

echo -n "Getting manifest, cutting it down to size..." >&2
wget "https://ark2.spinitron.com/ark2/${remote_dirname}/index.m3u8" -O ${ORIGINAL_MANIFEST_NAME} >/dev/null 2>&1

awk '
   /seg-'${SHOW_LENGTH}'-a1\.ts/ {
      print($0)
      FLAG=1
   } 
   
   FLAG {
      next
   } 
   
   # fall-through case
   {
      print($0)
   }
   
   END {
      print("#EXT-X-ENDLIST")
   }' \
   ./index.m3u8 > "${NEW_MANIFEST_NAME}"
echo "done."

# turn off buffering in ffmpeg and track progress
ffmpeg  -protocol_whitelist "file,tcp,tls,https" \
        -i "${NEW_MANIFEST_NAME}" \
        "${local_filename}" 2>&1 \
   | stdbuf -i0 -o0 -e0 egrep -o 'seg-[[:digit:]].+\.ts' \
   | stdbuf -i0 -o0 -e0 -- pv -eta --progress --name "Reading fragments" -l -s ${SHOW_LENGTH} - \
   | cat >/dev/null

mid3v2 \
   --artist="Dave Wright, Falcotronik" \
   --album="Under Surveillance" \
   --genre="IDM Square-Dance and Atmospherics" \
   --date=${YEAR}-${MONTH}-${DAY} \
   --comment="Shout out as always to Armchair Lou and the Bimbos" \
   ${local_filename}

echo "Enjoy /Under Surveillance/!" >&2
exit 0