如何在正则表达式中匹配&或；或< or >或|？

Question

下面的正则表达式确认传入的输入是否包含字符串'ping‘

elsif($RunCommand =~ m/^\s*ping\s+(.+)/)

现在我想确认传递的输入是否包含管道命令|

以下内容似乎不能正常工作：

elsif($RunCommand =~ m/^\s*|\s+(.+)/)

对于上下文，我有以下if，elseif if子例程。我只是在它的顶部添加了检查&或；或<或>或|的5个语句。但它不能正常工作...现在它总是转到&PrintPageHeaderBC("c")；，并且包含ping、nslookup等(可接受的命令)的尝试现在不会执行它们应该执行的操作。我相信问题一定是我添加的5个正则表达式不能正确匹配输入的包含&或；或<或>或|的文本。有什么帮助吗？我确信我所做的5个单独的语句(可能是错误的)也可以组合成一个语句。

# First discard command attempts that contain & ; < > |, then acceptable commands are executed, then final else to non-functional command

 if($RunCommand =~ m/^\s*&\s+(.+)/)
    {
            # Print PageHeaderBC that informs of non-functional command
            &PrintPageHeaderBC("c");

    }

 elsif($RunCommand =~ m/^\s*;\s+(.+)/)
    {
            # Print PageHeaderBC that informs of non-functional command
            &PrintPageHeaderBC("c");

    }

 elsif($RunCommand =~ m/^\s*<\s+(.+)/)
    {
            # Print PageHeaderBC that informs of non-functional command
            &PrintPageHeaderBC("c");

    }

 elsif($RunCommand =~ m/^\s*>\s+(.+)/)
    {
            # Print PageHeaderBC that informs of non-functional command
            &PrintPageHeaderBC("c");

    }

 elsif($RunCommand =~ m/^\s*|\s+(.+)/)
    {
            # Print PageHeaderBC that informs of non-functional command
            &PrintPageHeaderBC("c");

    }

# Now start acceptable commands

# PING
elsif($RunCommand =~ m/^\s*ping\s+(.+)/)
{
    &PrintPageHeader("c");
            #$Prompt = $WinNT ? "$CurrentDir> " : "[admin\@$ServerName $CurrentDir]\$ ";
            $Prompt = $WinNT ? "$CurrentDir> " : "\$ ";
            print "<code>$Prompt $RunCommand</code><xmp>";
            $Command = "cd \"$CurrentDir\"".$CmdSep.$RunCommand.$Redirector;
            if(!$WinNT)
            {
                    $SIG{'ALRM'} = \&CommandTimeout;
                    alarm($CommandTimeoutDuration);
            }
            if($ShowDynamicOutput) # show output as it is generated
            {
                    $|=1;
                    $Command .= " |";
                    open(CommandOutput, $Command);
                    while(<CommandOutput>)
                    {
                            $_ =~ s/(\n|\r\n)$//;
                            print "$_\n";
                    }
                    $|=0;
            }
            else # show output after command completes
            {
                    print `$Command`;
            }
            if(!$WinNT)
            {
                    alarm(0);
            }
            print "</xmp>";

}
# TELNET
elsif($RunCommand =~ m/^\s*telnet\s+(.+)/)
{
    &PrintPageHeader("c");
    #$Prompt = $WinNT ? "$CurrentDir> " : "[admin\@$ServerName $CurrentDir]\$ ";
    $Prompt = $WinNT ? "$CurrentDir> " : "\$ ";
    print "<code>$Prompt $RunCommand</code><xmp>";
    $Command = "cd \"$CurrentDir\"".$CmdSep.$RunCommand.$Redirector;
    if(!$WinNT)
    {
        $SIG{'ALRM'} = \&CommandTimeout;
        alarm($CommandTimeoutDuration);
    }
    if($ShowDynamicOutput) # show output as it is generated
    {
        $|=1;
        $Command .= " |";
        open(CommandOutput, $Command);
        while(<CommandOutput>)
        {
            $_ =~ s/(\n|\r\n)$//;
            print "$_\n";
        }
        $|=0;
    }
    else # show output after command completes
    {
        print `$Command`;
    }
    if(!$WinNT)
    {
        alarm(0);
    }
    print "</xmp>";
}
#DIG
elsif($RunCommand =~ m/^\s*dig\s+(.+)/)
    {
            &PrintPageHeader("c");
            #$Prompt = $WinNT ? "$CurrentDir> " : "[admin\@$ServerName $CurrentDir]\$ ";
            $Prompt = $WinNT ? "$CurrentDir> " : "\$ ";
            print "<code>$Prompt $RunCommand</code><xmp>";
            $Command = "cd \"$CurrentDir\"".$CmdSep.$RunCommand.$Redirector;
            if(!$WinNT)
            {
                    $SIG{'ALRM'} = \&CommandTimeout;
                    alarm($CommandTimeoutDuration);
            }
            if($ShowDynamicOutput) # show output as it is generated
            {
                    $|=1;
                    $Command .= " |";
                    open(CommandOutput, $Command);
                    while(<CommandOutput>)
                    {
                            $_ =~ s/(\n|\r\n)$//;
                            print "$_\n";
                    }
                    $|=0;
            }
            else # show output after command completes
            {
                    print `$Command`;
            }
            if(!$WinNT)
            {
                    alarm(0);
            }
            print "</xmp>";
    }
#NSLOOKUP
elsif($RunCommand =~ m/^\s*nslookup\s+(.+)/)
    {
            &PrintPageHeader("c");
            #$Prompt = $WinNT ? "$CurrentDir> " : "[admin\@$ServerName $CurrentDir]\$ ";
            $Prompt = $WinNT ? "$CurrentDir> " : "\$ ";
            print "<code>$Prompt $RunCommand</code><xmp>";
            $Command = "cd \"$CurrentDir\"".$CmdSep.$RunCommand.$Redirector;
            if(!$WinNT)
            {
                    $SIG{'ALRM'} = \&CommandTimeout;
                    alarm($CommandTimeoutDuration);
            }
            if($ShowDynamicOutput) # show output as it is generated
            {
                    $|=1;
                    $Command .= " |";
                    open(CommandOutput, $Command);
                    while(<CommandOutput>)
                    {
                            $_ =~ s/(\n|\r\n)$//;
                            print "$_\n";
                    }
                    $|=0;
            }
            else # show output after command completes
            {
                    print `$Command`;
            }
            if(!$WinNT)
            {
                    alarm(0);
            }
            print "</xmp>";
    }

#HOST
elsif($RunCommand =~ m/^\s*host\s+(.+)/)
    {
            &PrintPageHeader("c");
            #$Prompt = $WinNT ? "$CurrentDir> " : "[admin\@$ServerName $CurrentDir]\$ ";
            $Prompt = $WinNT ? "$CurrentDir> " : "\$ ";
            print "<code>$Prompt $RunCommand</code><xmp>";
            $Command = "cd \"$CurrentDir\"".$CmdSep.$RunCommand.$Redirector;
            if(!$WinNT)
            {
                    $SIG{'ALRM'} = \&CommandTimeout;
                    alarm($CommandTimeoutDuration);
            }
            if($ShowDynamicOutput) # show output as it is generated
            {
                    $|=1;
                    $Command .= " |";
                    open(CommandOutput, $Command);
                    while(<CommandOutput>)
                    {
                            $_ =~ s/(\n|\r\n)$//;
                            print "$_\n";
                    }
                    $|=0;
            }
            else # show output after command completes
            {
                    print `$Command`;
            }
            if(!$WinNT)
            {
                    alarm(0);
            }
            print "</xmp>";
    }

#NMAP
elsif($RunCommand =~ m/^\s*nmap\s+(.+)/)
    {
            &PrintPageHeader("c");
            #$Prompt = $WinNT ? "$CurrentDir> " : "[admin\@$ServerName $CurrentDir]\$ ";
            $Prompt = $WinNT ? "$CurrentDir> " : "\$ ";
            print "<code>$Prompt $RunCommand</code><xmp>";
            $Command = "cd \"$CurrentDir\"".$CmdSep.$RunCommand.$Redirector;
            if(!$WinNT)
            {
                    $SIG{'ALRM'} = \&CommandTimeout;
                    alarm($CommandTimeoutDuration);
            }
            if($ShowDynamicOutput) # show output as it is generated
            {
                    $|=1;
                    $Command .= " |";
                    open(CommandOutput, $Command);
                    while(<CommandOutput>)
                    {
                            $_ =~ s/(\n|\r\n)$//;
                            print "$_\n";
                    }
                    $|=0;
            }
            else # show output after command completes
            {
                    print `$Command`;
            }
            if(!$WinNT)
            {
                    alarm(0);
            }
            print "</xmp>";
    }

#TRACEROUTE
    elsif($RunCommand =~ m/^\s*traceroute\s+(.+)/)
    {
            &PrintPageHeader("c");
            #$Prompt = $WinNT ? "$CurrentDir> " : "[admin\@$ServerName $CurrentDir]\$ ";
            $Prompt = $WinNT ? "$CurrentDir> " : "\$ ";
            print "<code>$Prompt $RunCommand</code><xmp>";
            $Command = "cd \"$CurrentDir\"".$CmdSep.$RunCommand.$Redirector;
            if(!$WinNT)
            {
                    $SIG{'ALRM'} = \&CommandTimeout;
                    alarm($CommandTimeoutDuration);
            }
            if($ShowDynamicOutput) # show output as it is generated
            {
                    $|=1;
                    $Command .= " |";
                    open(CommandOutput, $Command);
                    while(<CommandOutput>)
                    {
                            $_ =~ s/(\n|\r\n)$//;
                            print "$_\n";
                    }
                    $|=0;
            }
            else # show output after command completes
            {
                    print `$Command`;
            }
            if(!$WinNT)
            {
                    alarm(0);
            }
            print "</xmp>";
    }

#WHOIS
    elsif($RunCommand =~ m/^\s*whois\s+(.+)/)
    {
            &PrintPageHeader("c");
            #$Prompt = $WinNT ? "$CurrentDir> " : "[admin\@$ServerName $CurrentDir]\$ ";
            $Prompt = $WinNT ? "$CurrentDir> " : "\$ ";
            print "<code>$Prompt $RunCommand</code><xmp>";
            $Command = "cd \"$CurrentDir\"".$CmdSep.$RunCommand.$Redirector;
            if(!$WinNT)
            {
                    $SIG{'ALRM'} = \&CommandTimeout;
                    alarm($CommandTimeoutDuration);
            }
            if($ShowDynamicOutput) # show output as it is generated
            {
                    $|=1;
                    $Command .= " |";
                    open(CommandOutput, $Command);
                    while(<CommandOutput>)
                    {
                            $_ =~ s/(\n|\r\n)$//;
                            print "$_\n";
                    }
                    $|=0;
            }
            else # show output after command completes
            {
                    print `$Command`;
            }
            if(!$WinNT)
            {
                    alarm(0);
            }
            print "</xmp>";
    }

else
{
            # Print PageHeaderBC that informs of non-functional command
    &PrintPageHeaderBC("c");

    }
&PrintCommandLineInputForm;
&PrintPageFooter;

}

Answer 1

在正则表达式中，|符号用于alternation。如果想要匹配文字|字符，则需要对其进行转义：

m/^\s*\|\s+(.+)/

此外，如果我要冒险猜测，我会说它总是落入“失败”子例程的原因是因为那个正则表达式。通过交替(如所写的)，它可以匹配任何以\s*或\s+(.+)开头的字符串，这实际上是由于\s*中的星号运算符而导致的任何字符串。

编辑：关于您的评论，由于锚定(^)，这些示例将不会与您的任何正则表达式匹配。如果我们以字符串ping 4.2.2.2; pwd为例，发生的情况是正则表达式引擎从字符串的开头开始匹配，因为它是锚定的。初始\s*通过重复零次来正确匹配，在这种情况下实际上什么也不做。然后它查找要匹配的;，但是下一个字符是4，因此它失败了。您提供的第二个字符串也是如此。由于您使用了\s+，如果;后面没有空格，它也会中断。

老实说，如果你真的只想阻止任何字符串，甚至包含字符<，>，;，|或&，最简单的事情是将它们都放入一个字符类中，并使用m/[&;|<>]/g进行匹配。因为这个正则表达式是未锚定的，所以它将在字符串中的任何位置匹配。但是，这将完全禁止这些字符，这意味着它们不能出现在字符串或任何类似的内容中。这可能不是您想要的，但它将应用于您当前声明的规则(“五个正则表达式应与包含&或；或<或>或|的任何文本匹配”)。

Answer 2

elsif($RunCommand =~ m/^\s*|\s+(.+)/)

需要满足以下条件：

elsif($RunCommand =~ m/^\s*\|\s+(.+)/)

|是正则表达式中的逻辑'or‘运算符，所以如果您试图匹配它，则需要对其进行转义

Answer 3

您需要使用\对特殊字符进行转义。例如，要搜索|，可以像这样对其进行转义，\|。因此，您的正则表达式匹配为：

m/^\s*\|\s+(.+)/

以下字符在regex中都有特殊含义，如果您希望按字面解释它们，则需要对它们进行转义：

* ? + [ ] ( ) { } ^ $ | \