linux - 使用 Shell 脚本防止在文件中输入重复记录

Question

我正在创建一个 sh 文件，用户在其中输入卷号、名称、主题名称和标记。我将它存储在一个文本文件中。现在我不希望用户再次输入相同的卷号。如果他输入相同的卷号，它应该抛出一条消息。这是我所做的:

read -p "Enter the roll: " roll
read -p "Enter the name: " name
read -p "Enter the Subject: " sub
read -p "Enter the mark: " mark
echo "$roll $name $sub $mark" >> asd.txt

如何防止输入重复的卷号。

Answer 1

touch asd.txt
rollExists=1
while [ $rollExists != 0 ]
do
    read -p "Enter the roll: " roll
    rollExists=`grep -e "^${roll} " asd.txt | wc -l`
    if [[ "$rollExists" != "0" ]]
    then
            echo "Roll already exists"
    fi
done
read -p "Enter the name: " name
read -p "Enter the Subject: " sub
read -p "Enter the mark: " mark
echo "$roll $name $sub $mark" >> asd.txt