Perl 提示用户输入，然后在相应字段中进行加减

我希望从

$a[3]

中减去变量

$cpySold

，并将其添加到

$a[4]

。我怎么做

目前我的输出如下：

Title:Alice in wonderland
Author:robert
No Of Copies Sold:*3*

Current Book Info:
Alice in wonderland, robert,$12.40,100,200

我怎么做下面这行？假设100-3=97，用户输入3份售出后，100+3=103

新书信息：罗伯特·爱丽丝梦游仙境，12.40,97203美元

---

我不喜欢在代码中混合使用shell和Perl，但这显然是出于教学原因，所以我们不得不忽略它

process_book_sold()
{
    read -p "Title: " title
    read -p "Author: " author
    read -p "No Of Copies Sold : " cpySold 
    if [ -n "$title" -a -n "$author" ]; then
        perl -ne '
            BEGIN{ $title = shift; $author = shift; $sales = shift; }
            @a = split /:/;
            if ($a[0] =~ m/$title/i and $a[1] =~ m/$author/i) 
            {
                 print "Current Book Info:\n";
                 print "$a[0], $a[1], $a[2], $a[3], $a[4]\n";
                 $a[3] -= $sales;
                 $a[4] += $sales;
                 print "New Book Info:\n";
                 print "$a[0], $a[1], $a[2], $a[3], $a[4]\n";
            }
            END{ print "\n" }' "$title" "$author" "$cpySold" /home/student/Downloads/BookDB.txt
    fi
}

除了将

pattern

重命名为

title

和

pattern1

重命名为

author

，此代码还将shell变量

$cpySold

传递给Perl。它还使用一种更简单的方法来检索前三个参数（只需从

shift

中捕获值）。

拆分

与以前相同。数据文件中的格式并不完全清楚，因为打印格式使用逗号而不是冒号来分隔字段

---

我只想用newbook info中的值替换

BookDB.txt

文件中的当前图书信息

我不相信这对你有任何好处（除非你自己尝试，否则你不会学到很多），但是

显然，这不是我第一次运行脚本，有时我会使用3以外的值来计算售出的拷贝数

通过显式文件管理，您可以编写：

process_book_sold()
{
    title="$1"
    author="$2"
    cpySold="$3"
    if [ -n "$title" -a -n "$author" ]; then
        perl -we '
            use strict;
            use English "-no_match_vars";
            my $title = shift;
            my $author = shift;
            my $sales = shift;
            my $file = shift;
            open my $fh, "+<", $file or die "Failed to open file $file for reading and writing";
            my $text;
            {
            local $/;
            $text = <$fh>;
            }
            chomp $text;
            my @a = split /:/, $text;
            print "Debug: @a\n";
            if ($a[0] =~ m/$title/i and $a[1] =~ m/$author/i) 
            {
                print "Current Book Info:\n";
                print "$a[0], $a[1], $a[2], $a[3], $a[4]\n";
                $a[3] -= $sales;
                $a[4] += $sales;
                print "New Book Info:\n";
                print "$a[0], $a[1], $a[2], $a[3], $a[4]\n";
                seek $fh, 0, 0;
                truncate $fh, 0;
                $OFS = ":";
                $ORS = "\n";
                print $fh @a;
            }
            close $fh;
            ' "$title" "$author" "$cpySold" BookDB.txt # /home/student/Downloads/BookDB.txt
    fi
}

# read -p "Title: " title
# read -p "Author: " author
# read -p "No Of Copies Sold : " cpySold 

process_book_sold "Alice in Wonderland" "Carroll" "7"

---

为什么要使用bash和perl？为什么不直接使用perl呢？这是赋值要求，如果数据包含100和200，那么是100的减法和200的加法，还是相反？（…Hmmm…好的；所需的输出指示从100减去，然后添加到200…）您的代码当前有一行

打印“$a[0]，$a[1]，\$$a[2]，$a[3]，$a[4]\n”

这让人费解：为什么对

$a[2]

进行不同的处理？您将从perl命令行初始化的变量的范围限制在BEGIN块，并且没有启用警告或strict来通知您所产生的问题。更准确地说，我根本没有运行代码……但您是对的。@JonathanLeffler，很抱歉再次打扰您，我想获取新书信息并替换bookDB.txt中的当前图书信息，可以吗？您还没有真正显示文件的格式。特别是，它是包含一本书的一条记录，还是包含多本书的多条记录？是的，这是可能的。问题中没有足够的信息来说明什么是有意义的。（另外，格式是这样的，带有子标题的书籍不会整齐地存储-字段的冒号分隔符会被标题和子标题之间的冒号所混淆。然而，这可能也是本练习的给定内容。）bookDB.txt包含标题：author:price:qtyavailable:qtySold

process_book_sold()
{
    title="$1"
    author="$2"
    cpySold="$3"
    if [ -n "$title" -a -n "$author" ]
    then
        perl -i -we '
            use strict;
            use English "-no_match_vars";
            my $title = shift;
            my $author = shift;
            my $sales = shift;
            while (<>)
            {
                chomp;
                my @a = split /:/;
                print STDERR "Debug: @a\n";
                if ($a[0] =~ m/$title/i and $a[1] =~ m/$author/i) 
                {
                    print STDERR "Current Book Info:\n";
                    print STDERR "$a[0], $a[1], $a[2], $a[3], $a[4]\n";
                    $a[3] -= $sales;
                    $a[4] += $sales;
                    print STDERR "New Book Info:\n";
                    print STDERR "$a[0], $a[1], $a[2], $a[3], $a[4]\n";
                    $OFS = ":";
                    $ORS = "\n";
                    print @a;
                }
            }
            ' "$title" "$author" "$cpySold" BookDB.txt # /home/student/Downloads/BookDB.txt
    fi
}

#   read -p "Title: " title
#   read -p "Author: " author
#   read -p "No Of Copies Sold : " cpySold 
process_book_sold "Alice in Wonderland" "Carroll" "3"

$ cat BookDB.txt; bash pbs2.sh; cat BookDB.txt
Alice in Wonderland:Carroll:$12.40:74:226
Debug: Alice in Wonderland Carroll $12.40 74 226
Current Book Info:
Alice in Wonderland, Carroll, $12.40, 74, 226
New Book Info:
Alice in Wonderland, Carroll, $12.40, 71, 229
Alice in Wonderland:Carroll:$12.40:71:229
$

process_book_sold()
{
    title="$1"
    author="$2"
    cpySold="$3"
    if [ -n "$title" -a -n "$author" ]; then
        perl -we '
            use strict;
            use English "-no_match_vars";
            my $title = shift;
            my $author = shift;
            my $sales = shift;
            my $file = shift;
            open my $fh, "+<", $file or die "Failed to open file $file for reading and writing";
            my $text;
            {
            local $/;
            $text = <$fh>;
            }
            chomp $text;
            my @a = split /:/, $text;
            print "Debug: @a\n";
            if ($a[0] =~ m/$title/i and $a[1] =~ m/$author/i) 
            {
                print "Current Book Info:\n";
                print "$a[0], $a[1], $a[2], $a[3], $a[4]\n";
                $a[3] -= $sales;
                $a[4] += $sales;
                print "New Book Info:\n";
                print "$a[0], $a[1], $a[2], $a[3], $a[4]\n";
                seek $fh, 0, 0;
                truncate $fh, 0;
                $OFS = ":";
                $ORS = "\n";
                print $fh @a;
            }
            close $fh;
            ' "$title" "$author" "$cpySold" BookDB.txt # /home/student/Downloads/BookDB.txt
    fi
}

# read -p "Title: " title
# read -p "Author: " author
# read -p "No Of Copies Sold : " cpySold 

process_book_sold "Alice in Wonderland" "Carroll" "7"

$ cat BookDB.txt; bash pbs1.sh; cat BookDB.txt
Alice in Wonderland:Carroll:$12.40:50:250
Debug: Alice in Wonderland Carroll $12.40 50 250
Current Book Info:
Alice in Wonderland, Carroll, $12.40, 50, 250
New Book Info:
Alice in Wonderland, Carroll, $12.40, 43, 257
Alice in Wonderland:Carroll:$12.40:43:257
$