Question

shell中变量引用问题

fdisk -l 2> /dev/null | grep -o "Disk /dev/[sh]d[a-z]"
read -p "your choice: " PARTDISK

if [ $PARTDISK == 'quit' ];then
echo "quit"
exit 7
fi

until fdisk -l 2> /dev/null | grep -o "^Disk /dev/[sh]d[a-z]" | grep "Disk $PARTDISK$" &> /dev/null;do
read -p "wrong option,your choice again: " CHOICE
done

在
until fdisk -l 2> /dev/null | grep -o "^Disk /dev/[sh]d[a-z]" | grep "Disk $PARTDISK$" &> /dev/null;do
read -p "wrong option,your choice again: " CHOICE
done
段中，为什么 $PARTDISK$，而不是 $PARTDISK，用 $PARTDISK就过滤不出来

Answer 1

$PARTDISK代表变量名，$PARTDISK后的第二个$就是字符$,在grep中代表字符串的结束

没有那个$在$PARTDISK后还可以有其它字符，有了$只能选出$PARTDISK在字符串结尾的结果

追问

不用脚本，为什么直接给出命令fdisk -l 2> /dev/null | grep -o "^Disk /dev/[sh]d[a-z]" | grep "Disk $PARTDISK"却能过滤呢？