如何使用sed在文本文件中查找相应的位置并更新它的shell

Question

Book name:author:price:Qty:Qty Sold
==================================
harry potter:james:12.99:197:101
===============================

我想在这种情况下更新值为197的QTY，但我似乎无法用我的程序更新值，请帮助我，因为我刚开始学习shell编程。感谢

function update_qty_available
{
grep -c "$title:$author" BookDB.txt > /dev/null # Look for a line with matching values

if [ $? == 0 ]; 
then # If found then offer to change Qty
echo "Update Qty to what?"
read newQty
sed -i "s/\($title:$author\):[^:]:[^:]*:/\1:$newQty/" BookDB.txt
    echo "Book's Qty has been updated successfully!"
fi

Answer 1

在第一个字符类之后，你错过了一个星号。不要忘记扩大小组。

Answer 2

重构使用grep -q;修复if成语;将搜索锚定到行首;使用read -p代替单独的echo;抓住parens里面的价格，这样它就不会丢失;在正则表达式中添加缺少的重复;并在新的qty值后添加分隔符冒号;另外，添加一个else子句，以便该函数不会无声地失败。

function update_qty_available
{
    if grep -q "^$title:$author:" BookDB.txt
    then
        read -p "Update Qty to what?" newQty
        sed -i "s/^\($title:$author:[^:]*\):[^:]*:/\1:$newQty:/" BookDB.txt
        echo "Book's Qty has been updated successfully!"
    else
        echo "$0: BookDB.Txt: no '$title' by '$author'" >&2
    fi
}

Answer 3

以下是您对awk：

的处理方式

script.awk的内容：

BEGIN {
    FS=OFS=":"
    printf "Enter the book's name: "
    getline name < "-"
    printf "Enter author's name: "
    getline author < "-"
    printf "Enter new quantity: "
    getline newQty < "-"
}

$1==name && $2==author { $4=newQty }1

运行：

$ cat BookDB.txt 
Book name:author:price:Qty:Qty Sold
==================================
harry potter:james:12.99:197:101
===============================

$ awk -f script.awk BookDB.txt 
Enter the book's name: harry potter
Enter author's name: james
Enter new quantity: 5000
Book name:author:price:Qty:Qty Sold
==================================
harry potter:james:12.99:5000:101
===============================