在Bash脚本中避免MySQL读取竞争条件

I have an application to copy data off onto external disks. The copy requests are stored in a MySQL database and will be read from multiple copy machines, which run a bash script to pick up requests. Once a request is picked up, it is set as "inprogress" in the database. However, I'm trying to avoid a situation where multiple machines read the request close together and start copying the same data.I have an application to copy data off onto ext