如何修复“ ls：写错误：管道损坏”错误？

Question

在通过.php命令运行的screen文件中，出现ls: write error: Broken pipe错误，但脚本运行正常。我只是想解决该错误。我该如何解决？下面是我的代码段。

$execQuery = "mv -f `ls /home/MYSPORTS/MySPORTS/*.unl | head -500` /home/MYSPORTS/MySPORTS/OPERATION/ && awk -F'|' '{print $1 $2}' /home/MYSPORTS/MySPORTS/OPERATION/*.unl > /home/MYSPORTS/MySPORTS/OPERATION/scratch_card_unl.txt";
shell_exec($execQuery);