Voici le script... commentaires bienvenus.

Et bien-sûr, vous l'utilisez à vos risques et périls.

#! /bin/sh

#set -x

user=votre_user
password=votre_mdp

rm -f curl.headers
rm -f backup.php

curl -s -S -O -D curl.headers -d "login=$user&password=$password&check=1&all=1" http://sql.free.fr/backup.php
if [ $? -ne 0 ]
then
    echo "Erreur curl" >&2
    exit 1
else
	echo "Backup MySQL for $user OK"
fi

grep -q "HTTP/1.1 200 OK" curl.headers
if [ $? -eq 0 ]
then
    grep -q "Content-Disposition: attachment" curl.headers
    if [ $? -eq 0 ]
    then
	filename=$(grep "Content-Disposition: attachment" curl.headers | sed -e 's/.*filename="//' | sed -e 's/";.*$//')
	mv backup.php backup_mysql_$filename
	echo "Saved in backup_mysql_$filename"
    fi
    ls -1 backup_mysql_*.gz | sort -u | head -n-10 | xargs -r rm -v
else
	echo -n "Error : " >&2
	grep "HTTP/1.1 " curl.headers >&2
	exit 1
fi