用Shell语言写一个Linux服务器巡检脚本，巡检到异常，发送邮箱通知

好的，以下是一个Shell脚本示例，用于巡检Linux服务器并在发现异常时发送电子邮件通知。

#!/bin/bash

# set email recipient(s) 
email_recipient="your.email@example.com"

# set subject for email notification
subject="Linux Server Status Alert"

# get system uptime
uptime=$(uptime)

# check disk usage and send email if usage exceeds 80%
disk_usage=$(df -h | awk '{print $5 " " $6}' | sed 's/%//g')
while read -r output; do
  usage=$(echo $output | awk '{ print $1}' )
  partition=$(echo $output | awk '{ print $2}' )
  if [ $usage -ge 80 ]; then
    echo "WARNING: Disk usage for \"$partition\" is at $usage%"
    echo "WARNING: Disk usage for \"$partition\" is at $usage%" | mail -s "$subject" "$email_recipient"
  fi
done <<< "$disk_usage"

# check CPU usage and send email if usage exceeds 80%
cpu_usage=$(top -bn1 | grep load | awk '{printf "%.2f\n", $(NF-2)}')
if (( $(echo "$cpu_usage > 0.80" | bc -l) )); then
  echo "WARNING: CPU usage is at $cpu_usage%"
  echo "WARNING: CPU usage is at $cpu_usage%" | mail -s "$subject" "$email_recipient"
fi

# check memory usage and send email if usage exceeds 80%
mem_usage=$(free -m | awk '/Mem:/ { printf("%.2f"), $3/$2*100 }')
if (( $(echo "$mem_usage > 80" | bc -l) )); then
  echo "WARNING: Memory usage is at $mem_usage%"
  echo "WARNING: Memory usage is at $mem_usage%" | mail -s "$subject" "$email_recipient"
fi

# check for failed login attempts and send email if attempts exceed 5
failed_attempts=$(grep "Failed password" /var/log/auth.log | wc -l)
if [ $failed_attempts -ge 5 ]; then
  echo "WARNING: There have been $failed_attempts failed login attempts"
  echo "WARNING: There have been $failed_attempts failed login attempts" | mail -s "$subject" "$email_recipient"
fi

该脚本将检查磁盘使用情况、CPU使用情况、内存使用情况和失败的登录尝试，并在任何一项超过预设阈值时发送电子邮件警报。您需要将脚本中的电子邮件收件人和主题更改为适合您自己的值，并确保在服务器上安装了邮件客户端（例如sendmail或postfix）以便发送电子邮件。