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.\" ========================================================================
.\"
.IX Title "PERLFAQ9 1"
.TH PERLFAQ9 7 "2003-11-25" "perl v5.8.3" "Perl Programmers Reference Guide"
.SH "NAME"
perlfaq9 \- 網絡 (2003/01/31 17:36:57 )
.SH "DESCRIPTION 描述"
.IX Header "DESCRIPTION"
網絡通信，互聯網以及少量有關 web 的內容
.Sh "What is the correct form of response from a \s-1CGI\s0 script?"
.IX Subsection "一個 CGI 腳本的迴應的正確格式是什麼？"
(Alan Flavell <flavell+www@a5.ph.gla.ac.uk> answers...)
.PP
The Common Gateway Interface (\s-1CGI\s0) specifies a software interface between
a program (\*(L"\s-1CGI\s0 script\*(R") and a web server (\s-1HTTPD\s0). It is not specific
to Perl, and has its own FAQs and tutorials, and usenet group,
comp.infosystems.www.authoring.cgi
.PP
The original \s-1CGI\s0 specification is at: http://hoohoo.ncsa.uiuc.edu/cgi/
.PP
Current best-practice \s-1RFC\s0 draft at: http://CGI\-Spec.Golux.Com/
.PP
Other relevant documentation listed in: http://www.perl.org/CGI_MetaFAQ.html
.PP
These Perl FAQs very selectively cover some \s-1CGI\s0 issues. However, Perl
programmers are strongly advised to use the \s-1CGI\s0.pm module, to take care
of the details for them.
.PP
The similarity between \s-1CGI\s0 response headers (defined in the \s-1CGI\s0
specification) and \s-1HTTP\s0 response headers (defined in the \s-1HTTP\s0
specification, \s-1RFC2616\s0) is intentional, but can sometimes be confusing.
.PP
The \s-1CGI\s0 specification defines two kinds of script: the \*(L"Parsed Header\*(R"
script, and the \*(L"Non Parsed Header\*(R" (\s-1NPH\s0) script. Check your server
documentation to see what it supports. \*(L"Parsed Header\*(R" scripts are
simpler in various respects. The \s-1CGI\s0 specification allows any of the
usual newline representations in the \s-1CGI\s0 response (it's the server's
job to create an accurate \s-1HTTP\s0 response based on it). So \*(L"\en\*(R" written in
text mode is technically correct, and recommended. \s-1NPH\s0 scripts are more
tricky: they must put out a complete and accurate set of \s-1HTTP\s0
transaction response headers; the \s-1HTTP\s0 specification calls for records
to be terminated with carriage-return and line\-feed, i.e \s-1ASCII\s0 \e015\e012
written in binary mode.
.PP
Using \s-1CGI\s0.pm gives excellent platform independence, including \s-1EBCDIC\s0
systems. \s-1CGI\s0.pm selects an appropriate newline representation
($CGI::CRLF) and sets binmode as appropriate.
.Sh "我的 CGI 腳本從命令行執行正常，但是在瀏覽器中不行 (500 Server Error)。"
.IX Subsection "My CGI script runs from the command line but not the browser.  (500 Server Error)"
可能有很多事錯了。可以仔細閱讀 \*(L"Troubleshooting
Perl \s-1CGI\s0 scripts\*(R" guide, 位置是
.PP
.Vb 1
\&        http://www.perl.org/troubleshooting_CGI.html
.Ve
.PP
如果接下來，你能證明你已閱讀了 FAQ 並且你的問題不是那麼簡單，非叄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。表面上看似 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。
.PP
幾個實用的 FAQ，相關文檔和查錯嚮導列在 \s-1CGI\s0 Meta \s-1FAQ\s0 中：
.PP
.Vb 1
\&        http://www.perl.org/CGI_MetaFAQ.html
.Ve
.Sh "如何從 CGI 程序中得到好一點的錯誤提示？"
.IX Subsection "How can I get better error messages from a CGI program?"
Use the CGI::Carp module.  It replaces \f(CW\*(C`warn\*(C'\fR and \f(CW\*(C`die\*(C'\fR, plus the
normal Carp modules \f(CW\*(C`carp\*(C'\fR, \f(CW\*(C`croak\*(C'\fR, and \f(CW\*(C`confess\*(C'\fR functions with
more verbose and safer versions.  It still sends them to the normal
server error log.
.PP
.Vb 3
\&    use CGI::Carp;
\&    warn "This is a complaint";
\&    die "But this one is serious";
.Ve
.PP
The following use of CGI::Carp also redirects errors to a file of your choice,
placed in a \s-1BEGIN\s0 block to catch compile-time warnings as well:
.PP
.Vb 6
\&    BEGIN {
\&        use CGI::Carp qw(carpout);
\&        open(LOG, ">>/var/local/cgi-logs/mycgi-log")
\&            or die "Unable to append to mycgi-log: $!\en";
\&        carpout(*LOG);
\&    }
.Ve
.PP
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.
.PP
.Vb 2
\&    use CGI::Carp qw(fatalsToBrowser);
\&    die "Bad error here";
.Ve
.PP
Even if the error happens before you get the \s-1HTTP\s0 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 \f(CW\*(C`carpout\*(C'\fR) with the application name and date
stamp prepended.
.Sh "如何將字符串中的 HTML 刪除？"
.IX Subsection "How do I remove HTML from a string?"
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 \s-1HTML\s0，同時也試圖對結果文本進行簡單的格式化。
.PP
許多人嘗試用簡陋的正規表示式來解決這個問題，譬如說像 \f(CW\*(C`s/<.*?>//g\*(C'\fR，但這個式子在很多情況下會失敗，因爲要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，人們常忘了轉換如 < 的 entities（跳脫字 元\f(CW\*(C`&lt;\*(C'\fR）。
.PP
以下這個「簡陋」的方法對大多數的檔案都有效：
.PP
.Vb 2
\&    #!/usr/bin/perl -p0777
\&    s/<(?:[^>'"]*|(['"]).*?\e1)*>//gs
.Ve
.PP
如果您想要更完整的解法，請看叄部曲的 striphtml 程式，
http://www.cpan.org/authors/Tom_Christiansen/scripts/striphtml.gz
\&.
.PP
Here are some tricky cases that you should think about when picking
a solution:
.PP
.Vb 1
\&    <IMG SRC = "foo.gif" ALT = "A > B">
.Ve
.PP
.Vb 2
\&    <IMG SRC = "foo.gif"
\&         ALT = "A > B">
.Ve
.PP
.Vb 1
\&    <!-- <A comment> -->
.Ve
.PP
.Vb 1
\&    <script>if (a<b && a>c)</script>
.Ve
.PP
.Vb 1
\&    <# Just data #>
.Ve
.PP
.Vb 1
\&    <![INCLUDE CDATA [ >>>>>>>>>>>> ]]>
.Ve
.PP
If \s-1HTML\s0 comments include other tags, those solutions would also break
on text like this:
.PP
.Vb 3
\&    <!-- This section commented out.
\&        <B>You can't see me!</B>
\&    -->
.Ve
.Sh "如何萃取 URL?"
.IX Subsection "How do I extract URLs?"
可以簡單地從 HTML 中得到所有種類的 URL，只要使用 \f(CW\*(C`HTML::SimpleLinkExtor\*(C'\fR 模塊，它可以處理錨，圖像，對象，楨，其他包含 URL 的標籤。如果需要更復雜的東西，可以創建 \f(CW\*(C`HTML::LinkExtor\*(C'\fR 的子類或使用 \f(CW\*(C`HTML::Parser\*(C'\fR. 你甚至可以用
\&\f(CW\*(C`HTML::SimpleLinkExtor\*(C'\fR 作爲範例，來書寫適合你特殊需要的程序。
.PP
You can use URI::Find to extract URLs from an arbitrary text document.
.PP
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 \s-1HREF\s0 and there are no other attributes.
.PP
.Vb 7
\&        #!/usr/bin/perl -n00
\&        # qxurl - tchrist@perl.com
\&        print "$2\en" while m{
\&            < \es*
\&              A \es+ HREF \es* = \es* (["']) (.*?) \e1
\&            \es* >
\&        }gsix;
.Ve
.Sh "如何從用戶的機器上下載文件？如何打開其他機器上的文件？"
.IX Subsection "How do I download a file from the user's machine?  How do I open a file on another machine?"
In this case, download means to use the file upload feature of \s-1HTML\s0
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 \fBmultipart/form\-data\fR encoding.  The \s-1CGI\s0.pm module (which
comes with Perl as part of the Standard Library) supports this in the
\&\fIstart_multipart_form()\fR method, which isn't the same as the \fIstartform()\fR
method.
.PP
See the section in the \s-1CGI\s0.pm documentation on file uploads for code
examples and details.
.Sh "如何在 HTML 添加一個彈出菜單?"
.IX Subsection "How do I make a pop-up menu in HTML?"
用 <SELECT> 和 <OPTION>這兩個標籤。 CGI.pm模組（可由 CPAN取得）對這個 widget【此指跳出式選單這個介面成分】還有許多其他的介面成分都有支援【即有製作動態標籤的函式】，其中有些是以巧妙模擬的方 式達成。
.Sh "如何獲取 HTML 文件?"
.IX Subsection "How do I fetch an HTML file?"
有一個方法是，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：
.PP
.Vb 2
\&    $html_code = `lynx -source $url`;
\&    $text_data = `lynx -dump $url`;
.Ve
.PP
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，而且也不需要 lynx：
.PP
.Vb 3
\&    # simplest version
\&    use LWP::Simple;
\&    $content = get($URL);
.Ve
.PP
.Vb 3
\&    # or print HTML from a URL
\&    use LWP::Simple;
\&    getprint "http://www.linpro.no/lwp/";
.Ve
.PP
.Vb 11
\&    # 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;
.Ve
.Sh "如何根據提交的內容自動生成一個 HTML ?"
.IX Subsection "How do I automate an HTML form submission?"
If you're submitting values using the \s-1GET\s0 method, create a \s-1URL\s0 and encode
the form using the \f(CW\*(C`query_form\*(C'\fR method:
.PP
.Vb 2
\&    use LWP::Simple;
\&    use URI::URL;
.Ve
.PP
.Vb 3
\&    my $url = url('http://www.perl.com/cgi-bin/cpan_mod');
\&    $url->query_form(module => 'DB_File', readme => 1);
\&    $content = get($url);
.Ve
.PP
If you're using the \s-1POST\s0 method, create your own user agent and encode
the content appropriately.
.PP
.Vb 2
\&    use HTTP::Request::Common qw(POST);
\&    use LWP::UserAgent;
.Ve
.PP
.Vb 4
\&    $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;
.Ve
.Sh "如何解碼或創建 web 中的 %-encoding?"
.IX Subsection "How do I decode or create those %-encodings on the web?"
If you are writing a \s-1CGI\s0 script, you should be using the \s-1CGI\s0.pm module
that comes with perl, or some other equivalent module.  The \s-1CGI\s0 module
automatically decodes queries for you, and provides an \fIescape()\fR
function to handle encoding.
.PP
The best source of detailed information on \s-1URI\s0 encoding is \s-1RFC\s0 2396.
Basically, the following substitutions do it:
.PP
.Vb 1
\&    s/([^\ew()'*~!.-])/sprintf '%%%02x', ord $1/eg;   # encode
.Ve
.PP
.Vb 1
\&    s/%([A-Fa-f\ed]{2})/chr hex $1/eg;            # decode
.Ve
.PP
However, you should only apply them to individual \s-1URI\s0 components, not
the entire \s-1URI\s0, 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 \s-1RFC\s0, it's probably the best explanation there is.
.PP
\&\s-1RFC\s0 2396 also contains a lot of other useful information, including a
regexp for breaking any arbitrary \s-1URI\s0 into components (Appendix B).
.Sh "如何重定向到其他頁面？"
.IX Subsection "How do I redirect to another page?"
Specify the complete \s-1URL\s0 of the destination (even if it is on the same
server). This is one of the two different kinds of \s-1CGI\s0 \*(L"Location:\*(R"
responses which are defined in the \s-1CGI\s0 specification for a Parsed Headers
script. The other kind (an absolute URLpath) is resolved internally to
the server without any \s-1HTTP\s0 redirection. The \s-1CGI\s0 specifications do not
allow relative URLs in either case.
.PP
Use of \s-1CGI\s0.pm is strongly recommended.  This example shows redirection
with a complete \s-1URL\s0. This redirection is handled by the web browser.
.PP
.Vb 1
\&      use CGI qw/:standard/;
.Ve
.PP
.Vb 2
\&      my $url = 'http://www.cpan.org/';
\&      print redirect($url);
.Ve
.PP
This example shows a redirection with an absolute URLpath.  This
redirection is handled by the local web server.
.PP
.Vb 2
\&      my $url = '/CPAN/index.html';
\&      print redirect($url);
.Ve
.PP
But if coded directly, it could be as follows (the final \*(L"\en\*(R" is
shown separately, for clarity), using either a complete \s-1URL\s0 or
an absolute URLpath.
.PP
.Vb 2
\&      print "Location: $url\en";   # CGI response header
\&      print "\en";                 # end of headers
.Ve
.Sh "如何爲我的網頁加上密碼？"
.IX Subsection "How do I put a password on my web pages?"
要啓用 web 服務器的驗證，你需要配置你的 web 服務器，不同的服務器有不同的方法\-\-\-apache 與 iPlanet 不同，後者又與 \s-1IIS\s0 不同。從你的 web 服務器的文檔中查找特定服務器的配置細節。
.Sh "如何用 Perl 修改我的 .htpasswd 和 .htgroup 文件?"
.IX Subsection "How do I edit my .htpasswd and .htgroup files with Perl?"
HTTPD::UserAdmin 和 HTTPD::GroupAdmin 等模組爲這些檔案提供了統一的物件導向介面，儘管這些檔案可能以各種不同的格式儲存。這些資料庫可能是純文字格式、 dbm、Berkeley DB或任何 DBI相容的資料庫驅動程式 (drivers)。 HTTPD::UserAdmin支援`Basic' 和 `Digest'這兩個認證模式所用的檔案。以下是 一例：
.PP
.Vb 4
\&    use HTTPD::UserAdmin ();
\&    HTTPD::UserAdmin
\&          ->new(DB => "/foo/.htpasswd")
\&          ->add($username => $password);
.Ve
.Sh "如何確保用戶不會在表單中輸入使我的 CGI 腳本作壞事的值？"
.IX Subsection "How do I make sure users can't enter values into a form that cause my CGI script to do bad things?"
閱讀 \s-1CGI\s0 Meta \s-1FAQ\s0 列出的安全索引
.PP
.Vb 1
\&        http://www.perl.org/CGI_MetaFAQ.html
.Ve
.Sh "如何解釋一個郵件頭？"
.IX Subsection "How do I parse a mail header?"
要使用一個快速的方法，可以這樣使用 perlfunc 中的 \*(L"split\*(R" 函數：
.PP
.Vb 4
\&    $/ = '';
\&    $header = <MSG>;
\&    $header =~ s/\en\es+/ /g;      # 將延續行合併成單行
\&    %head = ( UNIX_FROM_LINE, split /^([-\ew]+):\es*/m, $header );
.Ve
.PP
但是，如果您若想保留所有 Received欄位資料的話【因 Received 欄位通常不止一個】，這個解法便不太行了。一個完整的解法是使用收錄在 CPAN的 Mail::Header 模組（ MailTools 套件的一部分）。
.Sh "如何解碼一個 CGI 表單？"
.IX Subsection "How do I decode a CGI form?"
使用標準模塊，應該是 \s-1CGI\s0.pm。沒有理由去嘗試手動去做！
.PP
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。這些程序都非常糟糕。他們僅在某些時候工作。他們通常不檢查 read() 的返回值，這是主要的錯誤。他們不處理 \s-1HEAD\s0 請求。他們不處理文件上載時的多成分表單。They don't deal
with \s-1GET/POST\s0 combinations where query fields are in more than one place.
They don't deal with keywords in the query string.
.PP
In short, they're bad hacks.  Resist them at all costs.  Please do not be
tempted to reinvent the wheel.  Instead, use the \s-1CGI\s0.pm or CGI_Lite.pm
(available from \s-1CPAN\s0), 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/ ).
.PP
Make sure you know whether to use a \s-1GET\s0 or a \s-1POST\s0 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 \s-1GET\s0 request
for a particular \s-1URL\s0 once or multiple times.  This is because the
\&\s-1HTTP\s0 protocol definition says that a \s-1GET\s0 request may be cached by the
browser, or server, or an intervening proxy.  \s-1POST\s0 requests cannot be
cached, because each request is independent and matters.  Typically,
\&\s-1POST\s0 requests change or depend on state on the server (query or update
a database, send mail, or purchase a computer).
.Sh "如何檢測一個有效的郵件地址？"
.IX Subsection "How do I check a valid mail address?"
沒有辦法。至少，沒有可行的辦法。
.PP
如果沒有寄封信到一個位址去試試看它會不會彈回來（即使是這麼做您還得面對停頓的問題），您是無法確定一個位址是否真的存在的。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，因爲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。
.PP
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.
.PP
許多人試圖用一個簡單的正規表示式，例如 \f(CW\*(C`/^[\ew.\-]+\e@(?:[\ew\-]+\e.)+\ew+$/\*(C'\fR 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，而且對測試一個位址有沒有希望投遞成功完全沒有幫助，所以在此建議大家不要這麼做；不過您可以看看：
http://www.cpan.org/authors/Tom_Christiansen/scripts/ckaddr.gz ,
這個 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。這個 script 跑起來不是很快，但至少有效。
.PP
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:
.PP
.Vb 1
\&    Dear someuser@host.com,
.Ve
.PP
.Vb 5
\&    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.
.Ve
.PP
If you get the message back and they've followed your directions,
you can be reasonably assured that it's real.
.PP
A related strategy that's less open to forgery is to give them a \s-1PIN\s0
(personal \s-1ID\s0 number).  Record the address and \s-1PIN\s0 (best that it be a
random one) for later processing.  In the mail you send, ask them to
include the \s-1PIN\s0 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 \s-1PIN\s0, such as
with the characters reversed, one added or subtracted to each digit, etc.
.Sh "如何解碼一個 MIME/BASE64 字符串?"
.IX Subsection "How do I decode a MIME/BASE64 string?"
MIME-tools套件（可自 CPAN取得）不但可處理這個問題而且有許多其他的功能。有了這個套件，解 BASE64碼就變得像這麼容易：
.PP
.Vb 2
\&    use MIME::Base64;
\&    $decoded = decode_base64($encoded);
.Ve
.PP
The MIME-Tools package (available from \s-1CPAN\s0) supports extraction with
decoding of \s-1BASE64\s0 encoded attachments and content directly from email
messages.
.PP
一個比較直接的解法是先做一點簡單的轉譯，然後使用 unpack()這個函數的 ``u'' 格式：
.PP
.Vb 4
\&    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
.Ve
.Sh "如何返回用戶的郵件地址？"
.IX Subsection "How do I return the user's mail address?"
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:
.PP
.Vb 2
\&    use Sys::Hostname;
\&    $address = sprintf('%s@%s', scalar getpwuid($<), hostname);
.Ve
.PP
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.
.PP
The Mail::Util module from \s-1CPAN\s0 (part of the MailTools package) provides a
\&\fImailaddress()\fR 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.
.Sh "如何發郵件？"
.IX Subsection "How do I send mail?"
Use the \f(CW\*(C`sendmail\*(C'\fR program directly:
.PP
.Vb 6
\&    open(SENDMAIL, "|/usr/lib/sendmail -oi -t -odq")
\&                        or die "Can't fork for sendmail: $!\en";
\&    print SENDMAIL <<"EOF";
\&    From: User Originating Mail <me\e@host>
\&    To: Final Destination <you\e@otherhost>
\&    Subject: A relevant subject line
.Ve
.PP
.Vb 4
\&    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";
.Ve
.PP
The \fB\-oi\fR option prevents sendmail from interpreting a line consisting
of a single dot as \*(L"end of message\*(R".  The \fB\-t\fR option says to use the
headers to decide who to send the message to, and \fB\-odq\fR 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.
.PP
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 \s-1SMTP\s0 daemon,
probably sendmail.
.PP
Or you might be able use the \s-1CPAN\s0 module Mail::Mailer:
.PP
.Vb 1
\&    use Mail::Mailer;
.Ve
.PP
.Vb 8
\&    $mailer = Mail::Mailer->new();
\&    $mailer->open({ From    => $from_address,
\&                    To      => $to_address,
\&                    Subject => $subject,
\&                  })
\&        or die "Can't open: $!\en";
\&    print $mailer $body;
\&    $mailer->close();
.Ve
.PP
The Mail::Internet module uses Net::SMTP which is less Unix-centric than
Mail::Mailer, but less reliable.  Avoid raw \s-1SMTP\s0 commands.  There
are many reasons to use a mail transport agent like sendmail.  These
include queuing, \s-1MX\s0 records, and security.
.Sh "如何使用 MIME 來爲郵件消息增加附件？"
.IX Subsection "How do I use MIME to make an attachment to a mail message?"
This answer is extracted directly from the MIME::Lite documentation.
Create a multipart message (i.e., one with attachments).
.PP
.Vb 1
\&    use MIME::Lite;
.Ve
.PP
.Vb 8
\&    ### 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'
\&                 );
.Ve
.PP
.Vb 8
\&    ### 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'
\&                 );
.Ve
.PP
.Vb 1
\&    $text = $msg->as_string;
.Ve
.PP
MIME::Lite also includes a method for sending these things.
.PP
.Vb 1
\&    $msg->send;
.Ve
.PP
This defaults to using sendmail but can be customized to use
\&\s-1SMTP\s0 via Net::SMTP.
.Sh "如何讀郵件？"
.IX Subsection "How do I read mail?"
While you could use the Mail::Folder module from \s-1CPAN\s0 (part of the
MailFolder package) or the Mail::Internet module from \s-1CPAN\s0 (part
of the MailTools package), often a module is overkill.  Here's a
mail sorter.
.PP
.Vb 1
\&    #!/usr/bin/perl
.Ve
.PP
.Vb 13
\&    my(@msgs, @sub);
\&    my $msgno = -1;
\&    $/ = '';                    # paragraph reads
\&    while (<>) {
\&        if (/^From /m) {
\&            /^Subject:\es*(?:Re:\es*)*(.*)/mi;
\&            $sub[++$msgno] = lc($1) || '';
\&        }
\&        $msgs[$msgno] .= $_;
\&    }
\&    for my $i (sort { $sub[$a] cmp $sub[$b] || $a <=> $b } (0 .. $#msgs)) {
\&        print $msgs[$i];
\&    }
.Ve
.PP
Or more succinctly,
.PP
.Vb 6
\&    #!/usr/bin/perl -n00
\&    # bysub2 - awkish sort-by-subject
\&    BEGIN { $msgno = -1 }
\&    $sub[++$msgno] = (/^Subject:\es*(?:Re:\es*)*(.*)/mi)[0] if /^From/m;
\&    $msg[$msgno] .= $_;
\&    END { print @msg[ sort { $sub[$a] cmp $sub[$b] || $a <=> $b } (0 .. $#msg) ] }
.Ve
.Sh "如何找到我的主機名/域名/IP 地址？"
.IX Subsection "How do I find out my hostname/domainname/IP address?"
長久以來許多 code都很草率地直接呼叫 `hostname` 這個程式來取得主機名。雖然這麼做很方便，但也同時增加了移植到其他平臺上的困難。這是一個很典型的例子，在方便和可移植性之間作抉擇，不論選哪一邊，必須付出一些犧牲和代價。
.PP
Sys::Hostname這個模組（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()這個系統呼叫來找出該機的 IP位址了（假定您的 DNS 運作正常）。
.PP
.Vb 4
\&    use Socket;
\&    use Sys::Hostname;
\&    my $host = hostname();
\&    my $addr = inet_ntoa(scalar gethostbyname($host || 'localhost'));
.Ve
.PP
至少在 Unix 底下，取得 DNS網域名最簡單的方法大概要算是直接從 /etc/resolv.conf 這個檔案裏面找。當然，這麼做的前提是 resolv.conf 這個檔案的設定必須照慣例的格式，還有就是這個檔案必先存在纔行。
.PP
(Perl在非 Unix系統下尚需要一有效的方法來測出機器和網域名)
.Sh "如何獲取一篇新聞文章或活動的新聞組？"
.IX Subsection "How do I fetch a news article or the active newsgroups?"
使用 Net::NNTP或 News::NNTPClient模組，兩者皆可自 CPAN下載。這些模組讓抓羣組名錄這類的差事變得這麼容易：
.PP
.Vb 2
\&    perl -MNews::NNTPClient
\&      -e 'print News::NNTPClient->new->list("newsgroups")'
.Ve
.Sh "如何獲取/上傳一個 FTP 文件?"
.IX Subsection "How do I fetch/put an FTP file?"
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）雖比較複雜，但可用來上傳、也能抓檔案。
.Sh "如何進行遠程過程調用 RPC ?"
.IX Subsection "How can I do RPC in Perl?"
模塊 \s-1DCE::RPC\s0 正在開發中 (但是還不可用)，將成爲 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，是一個 \s-1RPC\s0 存根生成器，包含一個 \s-1RPC::ONC\s0 模塊。
.SH "AUTHOR AND COPYRIGHT"
.IX Header "AUTHOR AND COPYRIGHT"
Copyright (c) 1997\-2002 Tom Christiansen and Nathan Torkington.
All rights reserved.
.PP
This documentation is free; you can redistribute it and/or modify it
under the same terms as Perl itself.
.PP
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.
.SH "譯者"
.B 蕭百齡，兩隻老虎工作室
.Sh "跋"
.br
本頁面中文版由中文 man 手冊頁計劃提供。
.br
中文 man 手冊頁計劃：\fBhttps://github.com/man-pages-zh/manpages-zh\fR