用正規表達式驗證郵件位址似乎是一件簡單的事情，但是如果要完美的驗證一個合規的郵件位址，其實也許很複雜。
其實，在産品環境中，一般來說并不需要這麼複雜的正規表達式來做到99.99%正确。一般來說，從執行效率和測試覆寫率來說，隻需要一個簡單的版本即可：
<code>/^[a-z0-9._%+-]+@[a-z0-9.-]+\.[a-z]{2,4}$/i</code>
那麼下面我們來看看這些更嚴謹、更複雜的正規表達式吧：
<a target="_blank"></a>
<code>(?:[a-z0-9!#$%&'*+/=?^_`{|}~-]+(?:\.[a-z0-9!#$%&'*+/=?^_`{|}~-]+)*|"(?:[\x01-\x08\x0b\x0c\x0e-\x1f\x21\x23-\x5b\x5d-\x7f]|\\[\x01-\x09\x0b\x0c\x0e-\x7f])*")@(?:(?:[a-z0-9](?:[a-z0-9-]*[a-z0-9])?\.)+[a-z0-9](?:[a-z0-9-]*[a-z0-9])?|\[(?:(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.){3}(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?|[a-z0-9-]*[a-z0-9]:(?:[\x01-\x08\x0b\x0c\x0e-\x1f\x21-\x5a\x53-\x7f]|\\[\x01-\x09\x0b\x0c\x0e-\x7f])+)\])</code>
由于各種語言對正規表達式的支援不同、文法差異和覆寫率不同，是以，不同語言裡面的正規表達式也不同：
這個是個簡單的版本：
<code>r"(^[a-za-z0-9_.+-]+@[a-za-z0-9-]+\.[a-za-z0-9-.]+$)"</code>
這個有點複雜了：
<code>/^[-a-z0-9~!$%^&*_=+}{\'?]+(\.[-a-z0-9~!$%^&*_=+}{\'?]+)*@([a-z0-9_][-a-z0-9_]*(\.[-a-z0-9_]+)*\.(aero|arpa|biz|com|coop|edu|gov|info|int|mil|museum|name|net|org|pro|travel|mobi|[a-z][a-z])|([0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}))(:[0-9]{1,5})?$/i</code>
<code>[a-z0-9a-z._%+-]+@[a-za-z0-9.-]+\\.[a-za-z]{2,6}</code>
php 的這個版本就更複雜了，覆寫率就更大一些：
<code>/^(?!(?:(?:\x22?\x5c[\x00-\x7e]\x22?)|(?:\x22?[^\x5c\x22]\x22?)){255,})(?!(?:(?:\x22?\x5c[\x00-\x7e]\x22?)|(?:\x22?[^\x5c\x22]\x22?)){65,}@)(?:(?:[\x21\x23-\x27\x2a\x2b\x2d\x2f-\x39\x3d\x3f\x5e-\x7e]+)|(?:\x22(?:[\x01-\x08\x0b\x0c\x0e-\x1f\x21\x23-\x5b\x5d-\x7f]|(?:\x5c[\x00-\x7f]))*\x22))(?:\.(?:(?:[\x21\x23-\x27\x2a\x2b\x2d\x2f-\x39\x3d\x3f\x5e-\x7e]+)|(?:\x22(?:[\x01-\x08\x0b\x0c\x0e-\x1f\x21\x23-\x5b\x5d-\x7f]|(?:\x5c[\x00-\x7f]))*\x22)))*@(?:(?:(?!.*[^.]{64,})(?:(?:(?:xn--)?[a-z0-9]+(?:-[a-z0-9]+)*\.){1,126}){1,}(?:(?:[a-z][a-z0-9]*)|(?:(?:xn--)[a-z0-9]+))(?:-[a-z0-9]+)*)|(?:\[(?:(?:ipv6:(?:(?:[a-f0-9]{1,4}(?::[a-f0-9]{1,4}){7})|(?:(?!(?:.*[a-f0-9][:\]]){7,})(?:[a-f0-9]{1,4}(?::[a-f0-9]{1,4}){0,5})?::(?:[a-f0-9]{1,4}(?::[a-f0-9]{1,4}){0,5})?)))|(?:(?:ipv6:(?:(?:[a-f0-9]{1,4}(?::[a-f0-9]{1,4}){5}:)|(?:(?!(?:.*[a-f0-9]:){5,})(?:[a-f0-9]{1,4}(?::[a-f0-9]{1,4}){0,3})?::(?:[a-f0-9]{1,4}(?::[a-f0-9]{1,4}){0,3}:)?)))?(?:(?:25[0-5])|(?:2[0-4][0-9])|(?:1[0-9]{2})|(?:[1-9]?[0-9]))(?:\.(?:(?:25[0-5])|(?:2[0-4][0-9])|(?:1[0-9]{2})|(?:[1-9]?[0-9]))){3}))\]))$/id</code>
對與 php 的版本，perl 和 ruby 表示不服，可以更嚴謹：
<code>(?:(?:\r\n)?[ \t])*(?:(?:(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+|\z|(?=[\["()<>@,;:\\".\[\]]))|"(?:[^\"\r\\]|\\.|(?:(?:\r\n)?[ \t]))*"(?:(?:\r\n)?[ \t])*)(?:\.(?:(?:\r\n)?[ \t])*(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+|\z|(?=[\["()<>@,;:\\".\[\]]))|"(?:[^\"\r\\]|\\.|(?:(?:\r\n)?[\t]))*"(?:(?:\r\n)?[ \t])*))*@(?:(?:\r\n)?[ \t])*(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+|\z|(?=[\["()<>@,;:\\".\[\]]))|\[([^\[\]\r\\]|\\.)*\](?:(?:\r\n)?[ \t])*)(?:\.(?:(?:\r\n)?[ \t])*(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+|\z|(?=[\["()<>@,;:\\".\[\]]))|\[([^\[\]\r\\]|\\.)*\](?:(?:\r\n)?[ \t])*))*|(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+|\z|(?=[\["()<>@,;:\\".\[\]]))|"(?:[^\"\r\\]|\\.|(?:(?:\r\n)?[ \t]))*"(?:(?:\r\n)?[ \t])*)*\<(?:(?:\r\n)?[ \t])*(?:@(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+|\z|(?=[\["()<>@,;:\\".\[\]]))|\[([^\[\]\r\\]|\\.)*\](?:(?:\r\n)?[\t])*)(?:\.(?:(?:\r\n)?[ \t])*(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+|\z|(?=[\["()<>@,;:\\".\[\]]))|\[([^\[\]\r\\]|\\.)*\](?:(?:\r\n)?[ \t])*))*(?:,@(?:(?:\r\n)?[ \t])*(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:\r\n)?[\t])+|\z|(?=[\["()<>@,;:\\".\[\]]))|\[([^\[\]\r\\]|\\.)*\](?:(?:\r\n)?[ \t])*)(?:\.(?:(?:\r\n)?[ \t])*(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+|\z|(?=[\["()<>@,;:\\".\[\]]))|\[([^\[\]\r\\]|\\.)*\](?:(?:\r\n)?[ \t])*))*)*:(?:(?:\r\n)?[ \t])*)?(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+|\z|(?=[\["()<>@,;:\\".\[\]]))|"(?:[^\"\r\\]|\\.|(?:(?:\r\n)?[ \t]))*"(?:(?:\r\n)?[ \t])*)(?:\.(?:(?:\r\n)?[ \t])*(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+|\z|(?=[\["()<>@,;:\\".\[\]]))|"(?:[^\"\r\\]|\\.|(?:(?:\r\n)?[ \t]))*"(?:(?:\r\n)?[ \t])*))*@(?:(?:\r\n)?[ \t])*(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+|\z|(?=[\["()<>@,;:\\".\[\]]))|\[([^\[\]\r\\]|\\.)*\](?:(?:\r\n)?[ \t])*)(?:\.(?:(?:\r\n)?[ \t])*(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+|\z|(?=[\["()<>@,;:\\".\[\]]))|\[([^\[\]\r\\]|\\.)*\](?:(?:\r\n)?[ \t])*))*\>(?:(?:\r\n)?[ \t])*)|(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+|\z|(?=[\["()<>@,;:\\".\[\]]))|"(?:[^\"\r\\]|\\.|(?:(?:\r\n)?[ \t]))*"(?:(?:\r\n)?[ \t])*)*:(?:(?:\r\n)?[ \t])*(?:(?:(?:[^()<>@,;:\\".\[\]\000-\031]+(?:(?:(?:\r\n)?[ \t])+|\z|(?=[\["()<>@,;:\\".\[\]]))|"(?:[^\"\r\\]|\\.|(?:(?:\r\n)?[ \t]))*"(?:(?:\r\n)?[ \t])*)(?:\.(?:(?:\r\n)?[ \t])*(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+|\z|(?=[\["()<>@,;:\\".\[\]]))|"(?:[^\"\r\\]|\\.|(?:(?:\r\n)?[ \t]))*"(?:(?:\r\n)?[ \t])*))*@(?:(?:\r\n)?[ \t])*(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+|\z|(?=[\["()<>@,;:\\".\[\]]))|\[([^\[\]\r\\]|\\.)*\](?:(?:\r\n)?[ \t])*)(?:\.(?:(?:\r\n)?[ \t])*(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+|\z|(?=[\["()<>@,;:\\".\[\]]))|\[([^\[\]\r\\]|\\.)*\](?:(?:\r\n)?[ \t])*))*|(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+|\z|(?=[\["()<>@,;:\\".\[\]]))|"(?:[^\"\r\\]|\\.|(?:(?:\r\n)?[ \t]))*"(?:(?:\r\n)?[ \t])*)*\<(?:(?:\r\n)?[ \t])*(?:@(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+|\z|(?=[\["()<>@,;:\\".\[\]]))|\[([^\[\]\r\\]|\\.)*\](?:(?:\r\n)?[ \t])*)(?:\.(?:(?:\r\n)?[ \t])*(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+|\z|(?=[\["()<>@,;:\\".\[\]]))|\[([^\[\]\r\\]|\\.)*\](?:(?:\r\n)?[ \t])*))*(?:,@(?:(?:\r\n)?[ \t])*(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+|\z|(?=[\["()<>@,;:\\".\[\]]))|\[([^\[\]\r\\]|\\.)*\](?:(?:\r\n)?[ \t])*)(?:\.(?:(?:\r\n)?[ \t])*(?:[^()<>@,;:\\".\[\]\000-\031]+(?:(?:(?:\r\n)?[ \t])+|\z|(?=[\["()<>@,;:\\".\[\]]))|\[([^\[\]\r\\]|\\.)*\](?:(?:\r\n)?[ \t])*))*)*:(?:(?:\r\n)?[ \t])*)?(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+|\z|(?=[\["()<>@,;:\\".\[\]]))|"(?:[^\"\r\\]|\\.|(?:(?:\r\n)?[ \t]))*"(?:(?:\r\n)?[ \t])*)(?:\.(?:(?:\r\n)?[ \t])*(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+|\z|(?=[\["()<>@,;:\\".\[\]]))|"(?:[^\"\r\\]|\\.|(?:(?:\r\n)?[ \t]))*"(?:(?:\r\n)?[ \t])*))*@(?:(?:\r\n)?[ \t])*(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+|\z|(?=[\["()<>@,;:\\".\[\]]))|\[([^\[\]\r\\]|\\.)*\](?:(?:\r\n)?[ \t])*)(?:\.(?:(?:\r\n)?[ \t])*(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+|\z|(?=[\["()<>@,;:\\".\[\]]))|\[([^\[\]\r\\]|\\.)*\](?:(?:\r\n)?[ \t])*))*\>(?:(?:\r\n)?[ \t])*)(?:,\s*(?:(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+|\z|(?=[\["()<>@,;:\\".\[\]]))|"(?:[^\"\r\\]|\\.|(?:(?:\r\n)?[ \t]))*"(?:(?:\r\n)?[ \t])*)(?:\.(?:(?:\r\n)?[ \t])*(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+|\z|(?=[\["()<>@,;:\\".\[\]]))|"(?:[^\"\r\\]|\\.|(?:(?:\r\n)?[ \t]))*"(?:(?:\r\n)?[ \t])*))*@(?:(?:\r\n)?[ \t])*(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+|\z|(?=[\["()<>@,;:\\".\[\]]))|\[([^\[\]\r\\]|\\.)*\](?:(?:\r\n)?[ \t])*)(?:\.(?:(?:\r\n)?[ \t])*(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+|\z|(?=[\["()<>@,;:\\".\[\]]))|\[([^\[\]\r\\]|\\.)*\](?:(?:\r\n)?[ \t])*))*|(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+|\z|(?=[\["()<>@,;:\\".\[\]]))|"(?:[^\"\r\\]|\\.|(?:(?:\r\n)?[ \t]))*"(?:(?:\r\n)?[ \t])*)*\<(?:(?:\r\n)?[ \t])*(?:@(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+|\z|(?=[\["()<>@,;:\\".\[\]]))|\[([^\[\]\r\\]|\\.)*\](?:(?:\r\n)?[ \t])*)(?:\.(?:(?:\r\n)?[ \t])*(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+|\z|(?=[\["()<>@,;:\\".\[\]]))|\[([^\[\]\r\\]|\\.)*\](?:(?:\r\n)?[ \t])*))*(?:,@(?:(?:\r\n)?[\t])*(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+|\z|(?=[\["()<>@,;:\\".\[\]]))|\[([^\[\]\r\\]|\\.)*\](?:(?:\r\n)?[ \t])*)(?:\.(?:(?:\r\n)?[ \t])*(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+|\z|(?=[\["()<>@,;:\\".\[\]]))|\[([^\[\]\r\\]|\\.)*\](?:(?:\r\n)?[ \t])*))*)*:(?:(?:\r\n)?[ \t])*)?(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+|\z|(?=[\["()<>@,;:\\".\[\]]))|"(?:[^\"\r\\]|\\.|(?:(?:\r\n)?[ \t]))*"(?:(?:\r\n)?[ \t])*)(?:\.(?:(?:\r\n)?[ \t])*(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+|\z|(?=[\["()<>@,;:\\".\[\]]))|"(?:[^\"\r\\]|\\.|(?:(?:\r\n)?[ \t]))*"(?:(?:\r\n)?[ \t])*))*@(?:(?:\r\n)?[ \t])*(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+|\z|(?=[\["()<>@,;:\\".\[\]]))|\[([^\[\]\r\\]|\\.)*\](?:(?:\r\n)?[ \t])*)(?:\.(?:(?:\r\n)?[ \t])*(?:[^()<>@,;:\\".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+|\z|(?=[\["()<>@,;:\\".\[\]]))|\[([^\[\]\r\\]|\\.)*\](?:(?:\r\n)?[ \t])*))*\>(?:(?:\r\n)?[ \t])*))*)?;\s</code>
上面的版本，嗯，我可以說是天書嗎？反正我是沒有解讀的想法了。當然，新版本的 perl 語言還有一個更易讀的版本（你是說真的麼？）
<code>/(?(define)</code>
<code>(?<address> (?&mailbox) | (?&group))</code>
<code>(?<mailbox> (?&name_addr) | (?&addr_spec))</code>
<code>(?<name_addr> (?&display_name)? (?&angle_addr))</code>
<code>(?<angle_addr> (?&cfws)? < (?&addr_spec) > (?&cfws)?)</code>
<code>(?<group> (?&display_name) : (?:(?&mailbox_list) | (?&cfws))? ;</code>
<code>(?&cfws)?)</code>
<code>(?<display_name> (?&phrase))</code>
<code>(?<mailbox_list> (?&mailbox) (?: , (?&mailbox))*)</code>
<code></code>
<code>(?<addr_spec> (?&local_part) \@ (?&domain))</code>
<code>(?<local_part> (?&dot_atom) | (?&quoted_string))</code>
<code>(?<domain> (?&dot_atom) | (?&domain_literal))</code>
<code>(?<domain_literal> (?&cfws)? \[ (?: (?&fws)? (?&dcontent))* (?&fws)?</code>
<code>\] (?&cfws)?)</code>
<code>(?<dcontent> (?&dtext) | (?&quoted_pair))</code>
<code>(?<dtext> (?&no_ws_ctl) | [\x21-\x5a\x5e-\x7e])</code>
<code>(?<atext> (?&alpha) | (?&digit) | [!#\$%&'*+-/=?^_`{|}~])</code>
<code>(?<atom> (?&cfws)? (?&atext)+ (?&cfws)?)</code>
<code>(?<dot_atom> (?&cfws)? (?&dot_atom_text) (?&cfws)?)</code>
<code>(?<dot_atom_text> (?&atext)+ (?: \. (?&atext)+)*)</code>
<code>(?<text> [\x01-\x09\x0b\x0c\x0e-\x7f])</code>
<code>(?<quoted_pair> \\ (?&text))</code>
<code>(?<qtext> (?&no_ws_ctl) | [\x21\x23-\x5b\x5d-\x7e])</code>
<code>(?<qcontent> (?&qtext) | (?&quoted_pair))</code>
<code>(?<quoted_string> (?&cfws)? (?&dquote) (?:(?&fws)? (?&qcontent))*</code>
<code>(?&fws)? (?&dquote) (?&cfws)?)</code>
<code>(?<word> (?&atom) | (?&quoted_string))</code>
<code>(?<phrase> (?&word)+)</code>
<code># folding white space</code>
<code>(?<fws> (?: (?&wsp)* (?&crlf))? (?&wsp)+)</code>
<code>(?<ctext> (?&no_ws_ctl) | [\x21-\x27\x2a-\x5b\x5d-\x7e])</code>
<code>(?<ccontent> (?&ctext) | (?&quoted_pair) | (?&comment))</code>
<code>(?<comment> \( (?: (?&fws)? (?&ccontent))* (?&fws)? \) )</code>
<code>(?<cfws> (?: (?&fws)? (?&comment))*</code>
<code>(?: (?:(?&fws)? (?&comment)) | (?&fws)))</code>
<code># no whitespace control</code>
<code>(?<no_ws_ctl> [\x01-\x08\x0b\x0c\x0e-\x1f\x7f])</code>
<code>(?<alpha> [a-za-z])</code>
<code>(?<digit> [0-9])</code>
<code>(?<crlf> \x0d \x0a)</code>
<code>(?<dquote> ")</code>
<code>(?<wsp> [\x20\x09])</code>
<code>)</code>
<code>(?&address)/x</code>
ruby 表示，其實人家還有個簡單版本：
這樣的版本誰沒有啊——.net 說：
<code>^\w+([-+.']\w+)*@\w+([-.]\w+)*\.\w+([-.]\w+)*$</code>
用 grep 指令在檔案中查找郵件位址，我想你不會寫個若幹行的正規表達式吧，意思一下就行了：
<code>$ grep -e -o "\b[a-za-z0-9._%+-]+@[a-za-z0-9.-]+\.[a-za-z]{2,6}\b" filename.txt</code>
在 sql server 中也是可以用正規表達式的，不過這個代碼片段應該是來自某個産品環境中的，是以，還體貼的照顧了那些把郵件位址寫錯的人：
<code>select email</code>
<code>from table_name where</code>
<code>patindex ('%[ &'',":;!+=\/()<>]%', email) > 0 -- invalid characters</code>
<code>or patindex ('[@.-_]%', email) > 0 -- valid but cannot be starting character</code>
<code>or patindex ('%[@.-_]', email) > 0 -- valid but cannot be ending character</code>
<code>or email not like '%@%.%' -- must contain at least one @ and one .</code>
<code>or email like '%..%' -- cannot have two periods in a row</code>
<code>or email like '%@%@%' -- cannot have two @ anywhere</code>
<code>or email like '%.@%' or email like '%@.%' -- cannot have @ and . next to each other</code>
<code>or email like '%.cm' or email like '%.co' -- camaroon or colombia? typos.</code>
<code>or email like '%.or' or email like '%.ne' -- missing last letter</code>
這個是不是有點偷懶？尤其是在那些“複雜”的正規表達式之後：
<code>from table_name</code>
<code>where regexp_like (email, '[a-z0-9._%-]+@[a-z0-9._%-]+\.[a-z]{2,4}');</code>
好吧，看來最後也一樣懶：
<code>select * from `users` where `email` not regexp '^[a-z0-9._%-]+@[a-z0-9.-]+\.[a-z]{2,4}$';</code>
那麼，你有沒有關于驗證郵件位址的正規表達式分享給大家？
<b>原文釋出時間為：2015-08-05</b>
<b></b>
<b>本文來自雲栖社群合作夥伴“linux中國</b>
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