字符串比较总是为真

Question

这是我目前拥有的代码。运行在 Perl v5.8.9 上。

#!/usr/bin/perl
# Prompts the user for their desired configuration
print "\n";
print "Please type BB for breadboard, or ACU for the Audio Control Unit.\n";
print "Do you want a BB or ACU version of alarm programmer: ";
$a = <STDIN>;
if($a == "ACU"){
    print("Initiating alarm programmer for ACU...\n");
}else{
    print("Initiating alarm programmer for breadboard...\n");
}

这是一些示例输出：

C:\Users\U157280\Documents\Alarm Programmer>PerlAutonomy.pl

Please type BB for breadboard, or ACU for the Audio Control Unit.
Do you want a BB or ACU version of alarm programmer: ACU

Initiating alarm programmer for ACU...

还有一个：

C:\Users\U157280\Documents\Alarm Programmer>PerlAutonomy.pl

Please type BB for breadboard, or ACU for the Audio Control Unit.
Do you want a BB or ACU version of alarm programmer: BB

Initiating alarm programmer for ACU...

如您所见，它为两者选择了 ACU，即使这些陈述看起来是正确的。

我做错了什么？

Answer 1

试试这个：

#!/usr/bin/perl
# Prompts the user for their desired configuration
print "\n";
print "Please type BB for breadboard, or ACU for the Audio Control Unit.\n";
print "Do you want a BB or ACU version of alarm programmer: ";
$a = <STDIN>;
chomp($a);
if($a eq "ACU"){
    print("Initiating alarm programmer for ACU...\n");
}else{
    print("Initiating alarm programmer for breadboard...\n");
}

您有两个问题，首先，= 是赋值而不是比较。其次，您在输入的末尾有一个您没有考虑的换行符。 chomp() 去掉换行符，eq 运算符进行字符串比较。

Answer 2

以下代码片段是 OP 修改后的代码，仅作了极少的更正。

请在您的脚本中包含 use strict; 和 use warnings，它会警告您有关代码的潜在问题——总之运行它将为您省去很多麻烦代码更正。

您应该使用字符串比较运算符 eq 而不是数字比较运算符 ==

#!/usr/bin/perl
#

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

# Prompts the user for their desired configuration
say  '
   Available options:

       BB  -- for breadboard
       ACU -- for the Audio Control Unit

';

print '   Please make a choice: ';

my $choice = <>;

chomp($choice);

if( $choice eq 'ACU') {
        say "\n  Initiating alarm programmer for ACU...";
} elsif( $choice eq 'BB' ) {
        say "\n  Initiating alarm programmer for breadboard...";
} else {
        say "\n  Wrong choice...";
}

exit 0;

要运行外部命令或脚本你应该使用system

参考：

字符串比较总是为真

String comparison is always true

string

perl