Make a file called getdb.sh.
#!/bin/bash
echo "Download keywords in kw.txt."
for kw in $(cat kw.txt)
do
curl http://www.mirbase.org/cgi-bin/get_seq.pl?acc=$kw > $kw.txt
done
Create another file called kw.txt:
MI0000342
MI0000343
MI0000344
Then run this
$ chmod +x getdb.sh
$ ./getdb.sh
Download keywords in kw.txt.
$ ls -1 *.txt
kw.txt
MI0000342.txt
MI0000343.txt
MI0000344.txt