cat > make_bigbed_mm39.sh <<'EOF'
#!/usr/bin/env bash
set -euo pipefail

# mm39 chrom sizes file you showed:
CS="/grid/bsr/data/data/utama/genome/GRCm39_M29_gencode/chrom.sizes"

# Convert each BED -> bigBed (BEDs here are bed3; we strip the track header)
for base in Tuft_CREs_ATAConly_200bp Tuft_CREs_H3K27aconly_500bp Tuft_CREs_overlap_200bp; do
  in="${base}.bed"
  tmp="${base}.sorted.bed"
  out="${base}.bb"

  echo "Converting $in -> $out"
  # drop header, sort, convert
  tail -n +2 "$in" | sort -k1,1 -k2,2n > "$tmp"
  bedToBigBed -type=bed3 "$tmp" "$CS" "$out"
  rm -f "$tmp"
done

chmod 644 Tuft_CREs_*.bb
echo "Done. Created: Tuft_CREs_*.bb"
EOF

chmod +x make_bigbed_mm39.sh