第一次尝试Linux，学习bash只是为了好玩。试着写一个脚本。
下面是我的一段代码（bash）：

sudo pacman -Suy | if grep --color=always -e "^" -e "there is nothing to do"; then pup=0; else pup=1; fi;

字符串
当我尝试回显变量时，什么也没有返回。我已经确认了变量根本没有被设置的多种方式。当我尝试在if语句中设置它时，echo $var工作得很好。
下面是我的一段很好的上下文代码：

case $yn in
        [yY] ) echo running only yay -Suy;
           echo running...;
           yay -Suy | if grep --color=always -e "^" -e "there is nothing to do"; then yup=0; else yup=1; fi; 
           break;;
        [nN] ) echo not updating;
           echo exiting...;
           exit;;
        [pP] ) running only pacman -Suy;
           echo running...;
           sudo pacman -Suy | if grep --color=always -e "^" -e "there is nothing to do"; then pup=0; else pup=1; fi;
           break;;
        [bB] ) echo running full sys update;
           echo running...;
           sudo pacman -Suy | if grep --color=always -e "^" -e "there is nothing to do"; then pup=0; else pup=1; fi; 
           yay -Suy | if grep --color=always -e "^" -e "there is nothing to do"; then yup=0; else yup=1; fi;
           break;;
        * ) echo invalid response;;
esac

done

if [ "$pup" -eq 1 ]; then
   echo "Pacman has updated something."
elif [ "$pup" -eq 0 ]; then
   echo "Pacman has not updated anything."
else
   :
fi
if [ "$yup" -eq 1 ]; then
   echo "Yay has updated something."
elif [ "$yup" -eq 0 ]; then
   echo "Yay has not updated anything."
else
   :
fi

型
当我用“echo '0'”替换pup=0时，它返回0没有问题。我试着修改最后一个if语句，没有变化。