使用mutt自动发送邮件

在测试邮件内容审查软件时，遇到频繁发送邮件的情况，索性写了个自动发送邮件的脚本。
使用方法是：将要发送的内容以下面的形式组织，

$ tree mails/
mails/
|-- mail1
|   |-- attach1
|   |-- attach2
|   |-- attach3
|   |-- attachment.lst
|   |-- body.txt
|   |-- receiver.lst
|   `-- subject.txt
|-- mail2
|   |-- attach1
|   |-- attach2
|   |-- attach3
|   |-- attachment.lst
|   |-- body.txt
|   |-- receiver.lst
|   `-- subject.txt
`-- mail3
|-- attach1
|-- attach2
|-- attach3
|-- attachment.lst
|-- body.txt
|-- receiver.lst
`-- subject.txt

其中receiver.lst是收件人列表，subject.txt是主题，body.txt是正文，attachment.lst是附件列表，attach1、attach2、attach3是attachment.lst中列出的附件，每个mailN文件夹是一封邮件。
脚本很简单：

#! /bin/bash
# Auto send email
#
if [[ $# < 1 ]]
then
echo "Usage: $0 "
exit
fi
DIR="$1"
cd "$DIR" || { echo "Enter $DIR failed"; exit; }
for dir in $(ls -d */)
do
cd "$dir" || { echo "Enter $dir failed"; continue; }
receiver=$(cat receiver.lst | sed ':a; $!N; s/\n/ /; ta')
subject=$(cat subject.txt)
body=$(cat body.txt)
attachment=$(cat attachment.lst | sed ':a; $!N; s/\n/ -a /; ta')
echo "$body" | mutt -s "$subject" -a $attachment $receiver
echo "Send $dir"
cd ..
done