the useful for loop

cp four_letter four_letter_bk

for i in `ls /media/10TB/Stats/Assembly_marker`
do
cd /media/10TB/Stats/Assembly_marker/${i}
v=`head -n 1 /media/10TB/Stats/index/four_letter`
mv *fasta ${v}.fasta
sed -i '1,1d' /media/10TB/Stats/index/four_letter
cd /media/10TB/Stats/Assembly_marker
done

for i in `ls /media/10TB/Stats/Assembly_marker`
do
readlink -f /media/10TB/Stats/Assembly_marker/${i}/*fasta >> /media/10TB/Stats.txt
done