Bash脚本 - 猫EOF打破

Question

我试图用猫EOF编写一个bash脚本来自动安装一个cron脚本，这部分是打破脚本，我不知道我要去哪里错了。出于某种原因，该脚本呼应之前运行这些命令/etc/no-ip.sh

echo "#!/bin/sh" >> /etc/no-ip.sh 
echo "HOSTNAME=hostname" >> /etc/no-ip.sh 
echo "LOGFILE=no-ip-log" >> /etc/no-ip.sh 
echo " " >> /etc/no-ip.sh 
echo "Current_IP=$(host $HOSTNAME | cut -f4 -d' ')" >> /etc/no-ip.sh 
echo " " >> /etc/no-ip.sh 
echo "if [ ! -s $LOGFILE ] ; then" >> /etc/no-ip.sh 
echo "echo "sshd : $Current_IP : allow" >> /etc/hosts.allow" >> /etc/no-ip.sh 
echo "echo $Current_IP > $LOGFILE" >> /etc/no-ip.sh 
echo "else" >> /etc/no-ip.sh 
echo " " >> /etc/no-ip.sh 
echo "Old_IP=`head -n 1 /etc/no-ip-log`" >> /etc/no-ip.sh 
echo " " >> /etc/no-ip.sh 
echo "if [ "$Current_IP" = "$Old_IP" ] ; then" >> /etc/no-ip.sh 
echo "echo IP address has not changed" >> /etc/no-ip.sh 
echo "else" >> /etc/no-ip.sh 
echo "sed -i 's/'$Old_IP'/'$Current_IP'/' /etc/hosts.allow" >> /etc/no-ip.sh 
echo "echo $Current_IP > $LOGFILE" >> /etc/no-ip.sh 
echo "echo iptables have been updated" >> /etc/no-ip.sh 
echo "fi" >> /etc/no-ip.sh 
echo "fi" >> /etc/no-ip.sh 
echo "EOF" >> /etc/no-ip.sh 

Answer 1

双引号仍然得到评估，如内部的某些东西：

echo "Current_IP=$(host $HOSTNAME | cut -f4 -d' ')" >> /etc/no-ip.sh 

在这里， $(...)结构被评估。所以你想在整个事情中使用单引号：

echo 'Current_IP=$(host $HOSTNAME | cut -f4 -d" ")' >> /etc/no-ip.sh 

和其他行相似。

---

也就是说，heredoc可能是写这个的更好方法。您需要引用您的分隔符字符串以便正文解释正文：

cat <<'EOF' > /etc/no-ip.sh 
... 
EOF