Byte order mark: Difference between revisions
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=== File command way === | === File command way === | ||
Using [https://en.wikipedia.org/wiki/File_(command) file (command)]: {{kbd | key=<nowiki>file filename.txt</nowiki>}} on {{Linux}}, {{Mac}}<ref>[https://developer.apple.com/legacy/library/documentation/Darwin/Reference/ManPages/man1/file.1.html file(1) Mac OS X Manual Page]</ref> & Cygwin on {{Win}} | Using [https://en.wikipedia.org/wiki/File_(command) file (command)]: {{kbd | key=<nowiki>file filename.txt</nowiki>}} on {{Linux}}, {{Mac}}<ref>[https://developer.apple.com/legacy/library/documentation/Darwin/Reference/ManPages/man1/file.1.html file(1) Mac OS X Manual Page]</ref> & Cygwin on {{Win}}. See details on [[Text file encoding]] | ||
== References == | == References == | ||
Revision as of 15:55, 21 October 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 |
If the column `id` was only allowed integer in column value, you can use the following sql query to find the records contains BOM:
SELECT * FROM `articles` WHERE HEX(`id`) REGEXP '[^0-9]+'
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
Excel / Google sheet way
Using the CODE function to check the "numeric code for the first character in a text string". If the cell A1 contains BOM,
- =CODE(A1) returns 63 on Excel 2016 of Win
[3] - =CODE(A1) returns 95 on Excel 2016 of macOS
- =CODE(A1) returns 65279 or other numeric value e.g. 28201 on Google sheet
File command way
Using file (command): file filename.txt on Linux 
, macOS [4] & Cygwin on Win 
. See details on Text file encoding