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NAME

       perlfaq9 - 網路 (2003/01/31 17:36:57 )

DESCRIPTIONyz
       網路通信,網際網路以及少量有關 web 的內容

       What is the correct form of response from a CGI script?

       (Alan Flavell <flavell+www@a5.ph.gla.ac.uk> answers...)

       The Common Gateway Interface (CGI) specifies a software interface
       between a program ("CGI script") and a web server (HTTPD). It is not
       specific to Perl, and has its own FAQs and tutorials, and usenet group,
       comp.infosystems.www.authoring.cgi

       The original CGI specification is at: http://hoohoo.ncsa.uiuc.edu/cgi/

       Current best-practice RFC draft at: http://CGI-Spec.Golux.Com/

       Other relevant documentation listed in:
       http://www.perl.org/CGI_MetaFAQ.html

       These Perl FAQs very selectively cover some CGI issues. However, Perl
       programmers are strongly advised to use the CGI.pm module, to take care
       of the details for them.

       The similarity between CGI response headers (defined in the CGI
       specification) and HTTP response headers (defined in the HTTP
       specification, RFC2616) is intentional, but can sometimes be confusing.

       The CGI specification defines two kinds of script: the "Parsed Header"
       script, and the "Non Parsed Header" (NPH) script. Check your server
       documentation to see what it supports. "Parsed Header" scripts are
       simpler in various respects. The CGI specification allows any of the
       usual newline representations in the CGI response (it's the server's
       job to create an accurate HTTP response based on it). So "\n" written
       in text mode is technically correct, and recommended. NPH scripts are
       more tricky: they must put out a complete and accurate set of HTTP
       transaction response headers; the HTTP specification calls for records
       to be terminated with carriage-return and line-feed, i.e ASCII \015\012
       written in binary mode.

       Using CGI.pm gives excellent platform independence, including EBCDIC
       systems. CGI.pm selects an appropriate newline representation
       ($CGI::CRLF) and sets binmode as appropriate.

       CGIZqRO`AObs (500 Server Error)http://www.perl.org/troubleshooting_CGI.html

       如果接下來,你能証明你已閱讀了 FAQ
       並且你的問題不是那麼簡單,非三言兩語即可回答的話,那麼您 post到
       comp.infosystems.www.authoring.cgi上(如果是有關 HTTP 、 HTML ,或
       CGI通信協定)的問題可能也會得到口氣和緩而有用的答覆。表惜W看似
       Perl,但骨子裏是 CGI之類的問題,如果 post到
       comp.lang.perl.misc人家可能就不會這麼樂意地接受了。

       幾蚢磪峈 FAQ,相關文件和查錯向導列在 CGI Meta FAQ 中:

               http://www.perl.org/CGI_MetaFAQ.html

      pq CGI{on@I~H

       Use the CGI::Carp module.  It replaces "warn" and "die", plus the
       normal Carp modules "carp", "croak", and "confess" functions with more
       verbose and safer versions.  It still sends them to the normal server
       error log.

           use CGI::Carp;
           warn "This is a complaint";
           die "But this one is serious";

       The following use of CGI::Carp also redirects errors to a file of your
       choice, placed in a BEGIN block to catch compile-time warnings as well:

           BEGIN {
               use CGI::Carp qw(carpout);
               open(LOG, ">>/var/local/cgi-logs/mycgi-log")
                   or die "Unable to append to mycgi-log: $!\n";
               carpout(*LOG);
           }

       You can even arrange for fatal errors to go back to the client browser,
       which is nice for your own debugging, but might confuse the end user.

           use CGI::Carp qw(fatalsToBrowser);
           die "Bad error here";

       Even if the error happens before you get the HTTP header out, the
       module will try to take care of this to avoid the dreaded server 500
       errors.  Normal warnings still go out to the server error log (or
       wherever you've sent them with "carpout") with the application name and
       date stamp prepended.

      pNr HTMLRH

       最正確(儘管不是最快)的方法是使用 HTML::Parse模組(可由
       CPAN取得,是所有寫 Web程式者必備的 libwww-perl
       套件的一部分)。另一中最正確的辦法是使用 HTML::FormatText,它不僅刪除了
       HTML,同時也試圖對結果文本進行簡單的格式化。

       許多人嘗試用簡悚漸興W表示式來解決這荌暋D,譬如說像 "s/<.*?>//g",但這-
       茼﹞l在很多情況下會失敗,因為-
       n處理的字串可能會跨越斷行字元,也可能含有被 quote【跳脫】的箭頭號,或有
       HTML comment出現;再加上一些疏忽,譬如,人戔`忘了轉換如 < 的
       entities(跳脫字 元"&lt;")。

       以下這荂u簡恣v的方法對大多數的檔案都有效:

           #!/usr/bin/perl -p0777
           s/<(?:[^>'"]*|(['"]).*?\1)*>//gs

       如果您想n更完整的解法,請看三部曲的 striphtml 程式,
       http://www.cpan.org/authors/Tom_Christiansen/scripts/striphtml.gz .

       Here are some tricky cases that you should think about when picking a
       solution:

           <IMG SRC = "foo.gif" ALT = "A > B">

           <IMG SRC = "foo.gif"
                ALT = "A > B">

           <!-- <A comment> -->

           <script>if (a<b && a>c)</script>

           <# Just data #>

           <![INCLUDE CDATA [ >>>>>>>>>>>> ]]>

       If HTML comments include other tags, those solutions would also break
       on text like this:

           <!-- This section commented out.
               <B>You can't see me!</B>
           -->

      p URL?

       可以簡單地從 HTML 中得到所有種類的 URL,只n使用 "HTML::SimpleLinkExtor"
       模塊,它可以處理錨,圖像,對象,楨,其他包含 URL 的標簽。如果需-
       n更復雜的東西,可以創建 "HTML::LinkExtor" 的子類或使用 "HTML::Parser".
       你甚至可以用 "HTML::SimpleLinkExtor" 作為範例,來書寫適合你特殊需-
       n的程式。

       You can use URI::Find to extract URLs from an arbitrary text document.

       Less complete solutions involving regular expressions can save you a
       lot of processing time if you know that the input is simple.  One
       solution from Tom Christiansen runs 100 times faster than most module
       based approaches but only extracts URLs from anchors where the first
       attribute is HREF and there are no other attributes.

               #!/usr/bin/perl -n00
               # qxurl - tchrist@perl.com
               print "$2\n" while m{
                   < \s*
                     A \s+ HREF \s* = \s* (["']) (.*?) \1
                   \s* >
               }gsix;

      pqWUHp}LWH

       In this case, download means to use the file upload feature of HTML
       forms.  You allow the web surfer to specify a file to send to your web
       server.  To you it looks like a download, and to the user it looks like
       an upload.  No matter what you call it, you do it with what's known as
       multipart/form-data encoding.  The CGI.pm module (which comes with Perl
       as part of the Standard Library) supports this in the
       start_multipart_form() method, which isn't the same as the startform()
       method.

       See the section in the CGI.pm documentation on file uploads for code
       examples and details.

      pb HTMLK[@uX?

       用 <SELECT> 和 <OPTION>這兩蚍陏情C CGI.pm模組(可由 CPAN取得)對這
       widget【此指跳出式選單這茪雇成分】還有許多其他的介-
       惘角應ㄕ酗銧屆i即有製作動態標簽的函式】,其中有些是以巧妙模擬的方
       式達成。

      p HTML?

       有一茪隤k是,如果您的系統上裝有 lynx一類的文字模式的
       HTML瀏覽器的話,那麼可以這麼做:

           $html_code = `lynx -source $url`;
           $text_data = `lynx -dump $url`;

       收錄在 CPAN裏的 libwww-perl
       (LWP)模組則提供了更強的方法來做這件事。它不但可鑽過
       proxies,而且也不需n lynx:

           # simplest version
           use LWP::Simple;
           $content = get($URL);

           # or print HTML from a URL
           use LWP::Simple;
           getprint "http://www.linpro.no/lwp/";

           # or print ASCII from HTML from a URL
           # also need HTML-Tree package from CPAN
           use LWP::Simple;
           use HTML::Parser;
           use HTML::FormatText;
           my ($html, $ascii);
           $html = get("http://www.perl.com/");
           defined $html
               or die "Can't fetch HTML from http://www.perl.com/";
           $ascii = HTML::FormatText->new->format(parse_html($html));
           print $ascii;

      pe@ HTML ?

       If you're submitting values using the GET method, create a URL and
       encode the form using the "query_form" method:

           use LWP::Simple;
           use URI::URL;

           my $url = url('http://www.perl.com/cgi-bin/cpan_mod');
           $url->query_form(module => 'DB_File', readme => 1);
           $content = get($url);

       If you're using the POST method, create your own user agent and encode
       the content appropriately.

           use HTTP::Request::Common qw(POST);
           use LWP::UserAgent;

           $ua = LWP::UserAgent->new();
           my $req = POST 'http://www.perl.com/cgi-bin/cpan_mod',
                          [ module => 'DB_File', readme => 1 ];
           $content = $ua->request($req)->as_string;

      pX web %-encoding?

       If you are writing a CGI script, you should be using the CGI.pm module
       that comes with perl, or some other equivalent module.  The CGI module
       automatically decodes queries for you, and provides an escape()
       function to handle encoding.

       The best source of detailed information on URI encoding is RFC 2396.
       Basically, the following substitutions do it:

           s/([^\w()'*~!.-])/sprintf '%%%02x', ord $1/eg;   # encode

           s/%([A-Fa-f\d]{2})/chr hex $1/eg;            # decode

       However, you should only apply them to individual URI components, not
       the entire URI, otherwise you'll lose information and generally mess
       things up.  If that didn't explain it, don't worry.  Just go read
       section 2 of the RFC, it's probably the best explanation there is.

       RFC 2396 also contains a lot of other useful information, including a
       regexp for breaking any arbitrary URI into components (Appendix B).

      pwVLH

       Specify the complete URL of the destination (even if it is on the same
       server). This is one of the two different kinds of CGI "Location:"
       responses which are defined in the CGI specification for a Parsed
       Headers script. The other kind (an absolute URLpath) is resolved
       internally to the server without any HTTP redirection. The CGI
       specifications do not allow relative URLs in either case.

       Use of CGI.pm is strongly recommended.  This example shows redirection
       with a complete URL. This redirection is handled by the web browser.

             use CGI qw/:standard/;

             my $url = 'http://www.cpan.org/';
             print redirect($url);

       This example shows a redirection with an absolute URLpath.  This
       redirection is handled by the local web server.

             my $url = '/CPAN/index.html';
             print redirect($url);

       But if coded directly, it could be as follows (the final "\n" is shown
       separately, for clarity), using either a complete URL or an absolute
       URLpath.

             print "Location: $url\n";   # CGI response header
             print "\n";                 # end of headers

      p[WKXH

       n啟用 web 伺服器的驗証,你需n配置你的 web
       伺服器,不同的伺服器有不同的方法---apache 與 iPlanet 不同,後者又與 IIS
       不同。從你的 web 伺服器的文件中查找特定伺服器的配置細節。

      p Perl .htpasswdM .htgroup?

       HTTPD::UserAdmin 和 HTTPD::GroupAdmin
       等模組為這些檔案提供了統一的物件導向介-
       情A儘管這些檔案可能以各種不同的格式儲存。這些資料庫可能是純文字格式、
       dbm、Berkeley DB或任何 DBI相容的資料庫驅動程式 (drivers)。
       HTTPD::UserAdmin支援`Basic' 和 `Digest'這兩蚖{証模式所用的檔案。以下是
       一例:

           use HTTPD::UserAdmin ();
           HTTPD::UserAdmin
                 ->new(DB => "/foo/.htpasswd")
                 ->add($username => $password);

      pTO|bJ CGIZ@aH

       閱讀 CGI Meta FAQ 列出的安全索引

               http://www.perl.org/CGI_MetaFAQ.html

      p@lYH

       n使用一荍硈t的方法,可以這樣使用 perlfunc 中的 "split" 函數:

           $/ = '';
           $header = <MSG>;
           $header =~ s/\n\s+/ /g;      # 將延續行合並成單行
           %head = ( UNIX_FROM_LINE, split /^([-\w]+):\s*/m, $header );

       但是,如果您Y想保留所有 Received欄位資料的話【因 Received
       欄位通常不止一荂j,這虒悛k便不太行了。一荍嗾膋爾悛k是使用收錄在 CPAN的
       Mail::Header 模組( MailTools 套件的一部分)。

      pX@ CGIH

       使用標準模塊,應該是 CGI.pm。沒有理由去嘗試手動去做!

       你大概都看過一大堆從 STDIN 讀取與 $ENV{CONTENT_LENGTH}
       長度相同的字節,或者獲取 $ENV{QUERY_STRING} 來解碼
       GET。這些程式都非常糟糕。他抾b某些時啎u作。他抭q常不檢查 read()
       的返回A這是主n的錯誤。他怳ㄢB理 HEAD 請求。他-
       怳ㄢB理檔案上載時的多成分表單。They don't deal with GET/POST
       combinations where query fields are in more than one place.  They don't
       deal with keywords in the query string.

       In short, they're bad hacks.  Resist them at all costs.  Please do not
       be tempted to reinvent the wheel.  Instead, use the CGI.pm or
       CGI_Lite.pm (available from CPAN), or if you're trapped in the module-
       free land of perl1 .. perl4, you might look into cgi-lib.pl (available
       from http://cgi-lib.stanford.edu/cgi-lib/ ).

       Make sure you know whether to use a GET or a POST in your form.  GETs
       should only be used for something that doesn't update the server.
       Otherwise you can get mangled databases and repeated feedback mail
       messages.  The fancy word for this is ``idempotency''.  This simply
       means that there should be no difference between making a GET request
       for a particular URL once or multiple times.  This is because the HTTP
       protocol definition says that a GET request may be cached by the
       browser, or server, or an intervening proxy.  POST requests cannot be
       cached, because each request is independent and matters.  Typically,
       POST requests change or depend on state on the server (query or update
       a database, send mail, or purchase a computer).

      p@la}H

       沒有辦法。至少,沒有可行的辦法。

       如果沒有寄封信到一茼鴔}去試試看它會不會彈回來(即使是這麼做您還得-
       措黻措y的問題),您是無法確定一茼鴔}是否真的存在的。即使您套用 email
       標頭的標準規格來做檢查的依據,您還是有可能會遇到問題,因為有些送得到的位址並不
       符合 RFC-822(電子郵件標頭的標準)的規定,但有些符合標準的位址卻無法投
       遞。

       You can use the Email::Valid or RFC::RFC822::Address which check the
       format of the address, although they cannot actually tell you if it is
       a deliverable address (i.e. that mail to the address will not bounce).
       Modules like Mail::CheckUser and Mail::EXPN try to interact with the
       domain name system or particular mail servers to learn even more, but
       their methods do not work everywhere---especially for security
       conscious administrators.

       許多人試圖用一蚋眾瑼漸興W表示式,例如 "/^[\w.-]+\@(?:[\w-]+\.)+\w+$/"
       來消除一些通常是無效的 email
       位址。不過,這樣做也把很多合格的位址給一起濾掉了,而且對測試一-
       茼鴔}有沒有希望投遞成功完全沒有幫助,所以在此建議大家不-
       n這麼做;不過您可以看看:
       http://www.cpan.org/authors/Tom_Christiansen/scripts/ckaddr.gz , 這
       script真的徹底地依據所有的 RFC規定來做檢驗(除了內嵌式
       comments外),同時會排除一些您可能不會想送信去的位址(如 Bill
       Clinton【美國總統】或您的
       postmaster),然後它會確定位址中的主機名稱可在 DNS中找得到。這 script
       跑起來不是很快,但至少有效。

       Our best advice for verifying a person's mail address is to have them
       enter their address twice, just as you normally do to change a
       password.  This usually weeds out typos.  If both versions match, send
       mail to that address with a personal message that looks somewhat like:

           Dear someuser@host.com,

           Please confirm the mail address you gave us Wed May  6 09:38:41
           MDT 1998 by replying to this message.  Include the string
           "Rumpelstiltskin" in that reply, but spelled in reverse; that is,
           start with "Nik...".  Once this is done, your confirmed address will
           be entered into our records.

       If you get the message back and they've followed your directions, you
       can be reasonably assured that it's real.

       A related strategy that's less open to forgery is to give them a PIN
       (personal ID number).  Record the address and PIN (best that it be a
       random one) for later processing.  In the mail you send, ask them to
       include the PIN in their reply.  But if it bounces, or the message is
       included via a ``vacation'' script, it'll be there anyway.  So it's
       best to ask them to mail back a slight alteration of the PIN, such as
       with the characters reversed, one added or subtracted to each digit,
       etc.

      pX@ MIME/BASE64r?

       MIME-tools套件(可自 CPAN取得)不但可處理這-
       荌暋D而且有許多其他的功能。有了這荇M件,解 BASE64碼就變得像這麼容易:

           use MIME::Base64;
           $decoded = decode_base64($encoded);

       The MIME-Tools package (available from CPAN) supports extraction with
       decoding of BASE64 encoded attachments and content directly from email
       messages.

       一茪騆直接的解法是先做一點簡單的轉譯,然後使用 unpack()這茖蝻 ``u''
       格式:

           tr#A-Za-z0-9+/##cd;                   # remove non-base64 chars
           tr#A-Za-z0-9+/# -_#;                  # convert to uuencoded format
           $len = pack("c", 32 + 0.75*length);   # compute length byte
           print unpack("u", $len . $_);         # uudecode and print

      p^la}H

       On systems that support getpwuid, the $< variable, and the
       Sys::Hostname module (which is part of the standard perl distribution),
       you can probably try using something like this:

           use Sys::Hostname;
           $address = sprintf('%s@%s', scalar getpwuid($<), hostname);

       Company policies on mail address can mean that this generates addresses
       that the company's mail system will not accept, so you should ask for
       users' mail addresses when this matters.  Furthermore, not all systems
       on which Perl runs are so forthcoming with this information as is Unix.

       The Mail::Util module from CPAN (part of the MailTools package)
       provides a mailaddress() function that tries to guess the mail address
       of the user.  It makes a more intelligent guess than the code above,
       using information given when the module was installed, but it could
       still be incorrect.  Again, the best way is often just to ask the user.

      polH

       Use the "sendmail" program directly:

           open(SENDMAIL, "|/usr/lib/sendmail -oi -t -odq")
                               or die "Can't fork for sendmail: $!\n";
           print SENDMAIL <<"EOF";
           From: User Originating Mail <me\@host>
           To: Final Destination <you\@otherhost>
           Subject: A relevant subject line

           Body of the message goes here after the blank line
           in as many lines as you like.
           EOF
           close(SENDMAIL)     or warn "sendmail didn't close nicely";

       The -oi option prevents sendmail from interpreting a line consisting of
       a single dot as "end of message".  The -t option says to use the
       headers to decide who to send the message to, and -odq says to put the
       message into the queue.  This last option means your message won't be
       immediately delivered, so leave it out if you want immediate delivery.

       Alternate, less convenient approaches include calling mail (sometimes
       called mailx) directly or simply opening up port 25 have having an
       intimate conversation between just you and the remote SMTP daemon,
       probably sendmail.

       Or you might be able use the CPAN module Mail::Mailer:

           use Mail::Mailer;

           $mailer = Mail::Mailer->new();
           $mailer->open({ From    => $from_address,
                           To      => $to_address,
                           Subject => $subject,
                         })
               or die "Can't open: $!\n";
           print $mailer $body;
           $mailer->close();

       The Mail::Internet module uses Net::SMTP which is less Unix-centric
       than Mail::Mailer, but less reliable.  Avoid raw SMTP commands.  There
       are many reasons to use a mail transport agent like sendmail.  These
       include queuing, MX records, and security.

      p MIMElW[H

       This answer is extracted directly from the MIME::Lite documentation.
       Create a multipart message (i.e., one with attachments).

           use MIME::Lite;

           ### Create a new multipart message:
           $msg = MIME::Lite->new(
                        From    =>'me@myhost.com',
                        To      =>'you@yourhost.com',
                        Cc      =>'some@other.com, some@more.com',
                        Subject =>'A message with 2 parts...',
                        Type    =>'multipart/mixed'
                        );

           ### Add parts (each "attach" has same arguments as "new"):
           $msg->attach(Type     =>'TEXT',
                        Data     =>"Here's the GIF file you wanted"
                        );
           $msg->attach(Type     =>'image/gif',
                        Path     =>'aaa000123.gif',
                        Filename =>'logo.gif'
                        );

           $text = $msg->as_string;

       MIME::Lite also includes a method for sending these things.

           $msg->send;

       This defaults to using sendmail but can be customized to use SMTP via
       Net::SMTP.

      plH

       While you could use the Mail::Folder module from CPAN (part of the
       MailFolder package) or the Mail::Internet module from CPAN (part of the
       MailTools package), often a module is overkill.  Here's a mail sorter.

           #!/usr/bin/perl

           my(@msgs, @sub);
           my $msgno = -1;
           $/ = '';                    # paragraph reads
           while (<>) {
               if (/^From /m) {
                   /^Subject:\s*(?:Re:\s*)*(.*)/mi;
                   $sub[++$msgno] = lc($1) || '';
               }
               $msgs[$msgno] .= $_;
           }
           for my $i (sort { $sub[$a] cmp $sub[$b] || $a <=> $b } (0 .. $#msgs)) {
               print $msgs[$i];
           }

       Or more succinctly,

           #!/usr/bin/perl -n00
           # bysub2 - awkish sort-by-subject
           BEGIN { $msgno = -1 }
           $sub[++$msgno] = (/^Subject:\s*(?:Re:\s*)*(.*)/mi)[0] if /^From/m;
           $msg[$msgno] .= $_;
           END { print @msg[ sort { $sub[$a] cmp $sub[$b] || $a <=> $b } (0 .. $#msg) ] }

      pDW//IPa}H

       長久以來許多 code都很草率地直接呼叫 `hostname` 這-
       茧{式來取得主機名。雖然這麼做很方便,但也同時增加了移植到其他-
       台上的困難。這是一茷雰憳洩漕狺l,在方便和可移植性之間作抉擇,不論選-
       一邊,必須付出一些犧牲和代價。

       Sys::Hostname這蚍珩捸]標準
       perl發行的一部分)可用來取得機器的名字,然後您便可利用
       gethostbyname()這茖t統呼叫來找出該機的 IP位址了(假定您的 DNS
       運作正常)。

           use Socket;
           use Sys::Hostname;
           my $host = hostname();
           my $addr = inet_ntoa(scalar gethostbyname($host || 'localhost'));

       至少在 Unix 底下,取得 DNS網域名最簡單的方法大概n算是直接從
       /etc/resolv.conf 這蚗仵釱堭找。當然,這麼做的前提是 resolv.conf 這-
       蚗仵蛌熙]定必須照慣例的格式,還有就是這蚗仵蚰畦存在才行。

       (Perl在非 Unix系統下尚需n一有效的方法來測出機器和網域名)

      p@gsDsDH

       使用 Net::NNTP或 News::NNTPClient模組,兩者皆可自
       CPAN下載。這些模組讓抓群組名錄這類的差事變得這麼容易:

           perl -MNews::NNTPClient
             -e 'print News::NNTPClient->new->list("newsgroups")'

      p/FTP?

       LWP::Simple模組(可自 CPAN下載)可以抓,但不能上傳檔案。
       Net::FTP模組(也可自 CPAN下載)雖比較復雜,但可用來上傳、也能抓檔案。

      pi{L{ RPC ?

       模塊 DCE::RPC 正在開發中 (但是還不可用),將成為 DCE-Perl 包 (可以從
       CPAN 下載) 的一部分。rpcgen 套件,可以從 CPAN/authors/id/JAKE/
       找到,是一 RPC 存根生成器,包含一 RPC::ONC 模塊。

AUTHOR AND COPYRIGHT

       Copyright (c) 1997-2002 Tom Christiansen and Nathan Torkington.  All
       rights reserved.

       This documentation is free; you can redistribute it and/or modify it
       under the same terms as Perl itself.

       Irrespective of its distribution, all code examples in this file are
       hereby placed into the public domain.  You are permitted and encouraged
       to use this code in your own programs for fun or for profit as you see
       fit.  A simple comment in the code giving credit would be courteous but
       is not required.

者
      Auu@室