Question

我有一个包含所有50个州的简单文本文件。我希望用户输入一个单词并让程序返回文件中特定状态所在的行，否则显示“未找到单词”消息。我不知道怎么用find。有人可以协助吗？这是我到目前为止所做的。

#!/bin/perl -w

open(FILENAME,"<WordList.txt");             #opens WordList.txt
my(@list) = <FILENAME>;                     #read file into list
my($state);                                 #create private "state"     variable
print "Enter a US state to search for: \n"; #Print statement
$line = <STDIN>;                            #use of STDIN to read input from user


close (FILENAME);

Answer 1

另一种解决方案，只读取文件的各个部分，直到找到结果或文件耗尽：

use strict;
use warnings; 

print "Enter a US state to search for: \n";
my $line = <STDIN>;
chomp($line);

# open file with 3 argument open (safer)
open my $fh, '<', 'WordList.txt'
   or die "Unable to open 'WordList.txt' for reading: $!";

# read the file until result is found or the file is exhausted
my $found = 0;
while ( my $row = <$fh> ) {
   chomp($row);
   next unless $row eq $line;

   # $. is a special variable representing the line number 
   # of the currently(most recently) accessed filehandle
   print "Found '$line' on line# $.\n"; 
   $found =  1;  # indicate that you found a result
   last;         # stop searching
}
close($fh);

unless ( $found ) { 
   print "'$line' was not found\n";
}

一般说明：

总是use strict;和use warnings;它们可以帮助您避免各种错误
通常首选3参数，以及or die ...语句。如果您无法打开文件，则从文件句柄中读取将失败
$。文档可以在perldoc perlvar

Answer 2

工作的工具是grep。

 chomp ( $line ); #remove linefeeds 
 print "$line is in list\n" if grep { m/^\Q$line\E$/g } @list;

您还可以将@list转换为哈希值，并使用map对其进行测试：

 my %cities = map { $_ => 1 } @list; 
 if ( $cities{$line} ) { print "$line is in list\n";}

注意 - 上面的内容，因为^和$的存在是完全匹配（并且区分大小写）。您可以轻松调整它以支持更模糊的场景。

当用户在Perl中输入文本时，如何找到单词所在的行？

2 个答案: