检查用户是否存在以bash发送的电子邮件

Question

我正在尝试创建一个脚本，提示用户输入用户名（在同一台UNIX服务器上），并检查该用户名是否存在，如果不存在则显示错误。< / p>

这是我到目前为止所做的：

#!/bin/bash
echo "Please enter the email address of the recipient and press <enter>: "
read recipient
echo "Please enter a subject for your message and press <enter>: "
read subject
mail -s "$subject" "$recipient"

我被告知我可以使用grep命令，我知道如何让grep显示用户名列表，但我不知道如何简单地检查脚本以查看名称是否有效

*编辑：

没关系，我发现了一些有用的东西：

echo "Please enter the email address of the recipient and press <enter>: "
read recipient
while [ -z "$(getent passwd $recipient)" ]
    do
        echo "invalid recipient"
        echo "Please enter the email address of the recipient and press <enter>: "
        read recipient
    done
        echo "Please enter a subject for your message and press <enter>: "
        read subject
        mail -s "$subject" "$recipient"
exit 0