regex - 使用正则表达式从字符串中提取匹配模式并使用 perl 将其分配给变量

Question

我正在寻求有关提取字符串部分的建议，这总是作为括号之间的第一个实例数据使用 perl 和正则表达式并将该值分配给变量。

这是确切的情况，我使用 perl 和 regex 从大学目录中提取 courseID 并将其分配给变量。请考虑以下事项:

BIO-2109-01 (12345) 生物学导论

CHM-3501-F2-01 (54321) 化学导论

IDS-3250-01 (98765) 美国历史 (1860-2000)

SPN-1234-02-F1 (45678) 西类牙历史 (1900-2010)

典型的格式是 [course-section-name] [(courseID)] [courseName]

我的目标是创建一个脚本，该脚本可以一次获取每个条目，将其分配给一个变量，然后使用正则表达式仅提取 courseID 并仅将 courseID 分配给变量。

我的方法是使用搜索和替换来替换与 '' 不匹配的所有内容，然后将剩下的内容(类(class) ID)保存到变量中。以下是我尝试过的一些示例:

$string = "BIO-2109-01 (12345) Introduction to Biology";
($courseID = $string) =~ s/[^\d\d\d\d\d]//g;
print $courseID;

结果:21090112345 --- 打印类(class)部分名称和类(class) ID

$string = "BIO-2109-01 (12345) Introduction to Biology";
$($courseID = $string) =~ s/[^\b\(\d{5}\)]\b//g;
print $courseID;

结果:210901(12345) --- 打印 course-section-name、parens 和 courseID

所以我在搜索和替换方面运气不佳 - 但是我发现了这个金块:

\(([^\)]+)\)

在 http://regexr.com/ 上将匹配括号部分。但是，它也会匹配多个参数，包括例如 (abc)。

我现在不太确定如何做这样的事情:

$string = "BIO-2109-01 (12345) Introduction to Biology";
($courseID = $string) =~ [magicRegex_goes_here];
print courseID;     

结果 12345

或更好:

$string = IDS-3250-01 (98765) History of US (1860-2000)
($courseID = $string) =~ [magicRegex_goes_here];
print courseID;

结果 98765

任何建议或方向将不胜感激。我已经尝试了我所知道的一切，并且可以研究正则表达式来解决这个问题。如果有更多信息我可以包括请询问。

更新

use warnings 'all';
use strict;
use feature 'say';

my $file = './data/enrollment.csv';      #File this script generates
my $course = "";                         #Complete course string [name-of-course] [(courseID)] [course_name]
my @arrayCourses = "";                   #Array of courseIDs
my $i = "";                              #i in for loop
my $courseID = "";                       #Extracted course ID
my $userName = "";                       #Username of person we are enrolling
my $action = "add,";                     #What we are doing to user
my $permission = "teacher,";             #What permissions to assign to user
my $stringToPrint = "";                  #Concatinated string to write to file
my $n = "\n";                            #\n
my $c = ",";                             #,

#BEGIN PROGRAM

print "Enter the username \n";

chomp($userName = <STDIN>);               #Get the enrollee username from user

print "\n";

print "Enter course name and press enter.  Enter 'x' to end. \n";  #prompt for course names

while ($course ne 'x') {
        chomp($course = <STDIN>);
        if ($course ne "x") {
                if (($courseID) = ($course =~ /[^(]+\(([^)]+)\)/) ) {     #nasty regex to extract courseID - thnx PerlDuck and zdim
                        push @arrayCourses, $courseID;                    #put the courseID into array
                }
                else {
                        print "Cannot process last entry check it";
                }
        }
        else {
                last;
        }
}

shift @arrayCourses;                      #Remove first entry from array - add,teacher,,username

open(my $fh,'>', $file);                  #open file

for $i (@arrayCourses)                    #write array to file
{
        $stringToPrint= join "", $action, $permission, $i, $c, $userName, $n ;
        print $fh $stringToPrint;
}

close $fh;

就可以了!随时欢迎提出建议或改进!感谢@PerlDuck 和@zdim

Answer 1

#!/usr/bin/env perl

use strict;
use warnings;

while( my $line = <DATA> ) {
    if (my ($courseID) = ($line =~ /[^(]+\(([^)]+)\)/) ) {
        print "course-ID = $courseID; -- line was $line";
    }
}

__DATA__
BIO-2109-01 (12345) Introduction to Biology
CHM-3501-F2-01 (54321) Introduction to Chemistry
IDS-3250-01 (98765) History of US (1860-2000)
SPN-1234-02-F1 (45678) Spanish History (1900-2010)

输出:

course-ID = 12345; -- line was BIO-2109-01 (12345) Introduction to Biology
course-ID = 54321; -- line was CHM-3501-F2-01 (54321) Introduction to Chemistry
course-ID = 98765; -- line was IDS-3250-01 (98765) History of US (1860-2000)
course-ID = 45678; -- line was SPN-1234-02-F1 (45678) Spanish History (1900-2010)

我使用的模式 /[^(]+\(([^)]+)\)/ 也可以写成

/ [^(]+     # 1 or more characters that are not a '('
  \(        # a literal '('. You must escape that because you don't want
            # to start it a capture group.
  ([^)]+)   # 1 or more chars that are not a ')'.
            # The sorrounding '(' and ')' capture this match
  \)        # a literal ')'
/x

/x 修饰符允许您在模式中插入空格、注释甚至换行符。

以防万一您不确定 /x 。你确实可以写:

while( my $line = <DATA> ) {
    if (my ($courseID) = ($line =~ / [^(]+   # …
                                     \(      # …
                                     ([^)]+) # …
                                     \)      # …
                                    /x ) ) {
        print "course-ID = $courseID; -- line was $line";
    }
}

这可能是 不好读 但你也可以将正则表达式存储在 单独的变量 中:

my $pattern = 
    qr/ [^(]+     # 1 or more characters that are not a '('
        \(        # a literal '(' (you must escape it)
        ([^)]+)   # 1 or more chars that are not a ')'.
                  # The sorrounding '(' and ')' capture this match
        \)        # a literal ')'
      /x;

进而:

if (my ($courseID) = ($line =~ $pattern)) {
    …
}