1. 清空文件内容

echo "" > "$work_path/upload.config"

cat /dev/null > $Off_upgrade_conf

2. 查看文件（多少行）

head -n 1 $work_path/upload.config | tail -n 1

tail -f -n 10 $work_path/upload.config

3. 写入数据到文件

echo "$host_do" >> "$work_path/upload.config"