Bash使用curl检查标题并在有任何错误时邮寄给我

Question

我正在尝试使用curl获取少数网站的标题，并在收到404,403,500,503等错误时发送邮件，但我一直收到此错误

错误：

line 7: [: -eq: unary operator expected

代码：

# !/bin/sh

NOW=$(date +"%H:%M_%m-%d-%Y")

web() {
    res=$(curl -I -s "$1" -o test/"$1_log_$NOW" | grep HTTP/1.1 | awk {'print $2'})
    if [ $res -eq 500 ]
    then
      echo "Error $res on $1" |mail -s "Error $res at $1 "mail@something.com

    fi
}

我设法做我想要的但是我改变了很多剧本：

#!/bin/sh

NOW=$(date +"%H:%M_%m-%d-%Y")

web() {

res=$(curl -I -s $1  | grep HTTP/1.1 | awk {'print $2'})
if [[ "$res" == 500 ||"$res" == 403 || "$res" == 404 ||"$res" == 503 ]]
then
  echo "Error $res on $1" |mail -s "Error $res at $1 " somethng@domain.com


fi
echo "$res" > /home/user/test/"$1_log_$NOW"

}
web domain1.com