Byte order mark: Difference between revisions
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[https://en.wikipedia.org/wiki/Byte_order_mark Byte order mark] (BOM, [https://zh.wikipedia.org/wiki/%E4%BD%8D%E5%85%83%E7%B5%84%E9%A0%86%E5%BA%8F%E8%A8%98%E8%99%9F 位元組順序記號]) | [https://en.wikipedia.org/wiki/Byte_order_mark Byte order mark] (BOM, [https://zh.wikipedia.org/wiki/%E4%BD%8D%E5%85%83%E7%B5%84%E9%A0%86%E5%BA%8F%E8%A8%98%E8%99%9F 位元組順序記號], 部分編輯器稱為「簽名」) | ||
== How to see Byte order mark == | == How to see Byte order mark == | ||
Revision as of 17:02, 25 April 2018
Byte order mark (BOM, 位元組順序記號, 部分編輯器稱為「簽名」)
How to see Byte order mark
MySQL way
Using MySQL HEX() function "returns a string representation of a hexadecimal value of a decimal or string value specified as an argument."
Run sql on sqlfiddle.com or Download the Sql file directly.
CREATE TABLE `articles` (
`id` varchar(50) NOT NULL,
`notes` text NOT NULL
) ENGINE=InnoDB DEFAULT CHARSET=utf8;
INSERT INTO `articles` (`id`, `notes`) VALUES
('1234567890', 'no BOM'),
('1234567890', 'BOM');
ALTER TABLE `articles`
ADD UNIQUE KEY `id` (`id`) USING BTREE;
SELECT HEX(id), id, notes FROM articles;
| HEX(id) | id | notes |
|---|---|---|
| 31323334353637383930 | 1234567890 | no BOM |
| EFBBBF31323334353637383930 | 1234567890 | BOM |
PHP way
$string = "1234567890";
echo $string . " NOT contains BOM --> after str2hex: " . str2hex($string) . PHP_EOL;
$string = "\xEF\xBB\xBF" . "1234567890";
echo $string . " contains BOM --> after str2hex: " . str2hex($string) . PHP_EOL;
function str2hex($string) {
$hexstr = unpack('H*', $string);
return array_shift($hexstr);
}
Result:
1234567890 NOT contains BOM --> after str2hex: 31323334353637383930 1234567890 contains BOM --> after str2hex: efbbbf31323334353637383930
File command way
Using file (command): file filename.txt on Linux 
, macOS 
[3] & Cygwin on Win 
| File content | Example result returned by file command |
|---|---|
| File contains BOM | UTF-8 Unicode (with BOM) text |
| File NOT contains BOM | UTF-8 Unicode text |