4/16/2023 0 Comments Notepad plusplus bf ide![]() ![]() Short answer: In UTF-8, a BOM is encoded as the bytes EF BB BF at the beginning of the file. What's different between UTF-8 and UTF-8 without BOM? I wanted to add more detailed info specifically about scripting and serialization, because it is an example of BOM characters causing real problems. Other uses of BOMĪs for the uses outside of JSON or scripts, I think there are already very good answers here. Adding BOMs even as an optional feature would only make it more complicated and error prone. If the only encodings are UTF-* and the first character must be an ASCII character lower than 128 then you already have all the information needed to determine both the encoding and the endianness of your data. Of course anyone is free to use things like BOMs or anything else if you need it - just don't call it JSON then.įor other data formats than JSON, take a look at how it really looks like. It should be a nobrainer to just not use it then and yet, there are always people who insist on breaking JSON by using BOMs, comments, different quoting rules or different data types. Other data formatsīOM in JSON is not needed, is illegal and breaks software that works correctly according to the RFC. UTF-16LE has only one NUL in the first four bytes, so it won't be recognizedĭepending on the implementation, all of those may be interpreted incorrectly as UTF-8 and then misinterpreted or rejected as invalid UTF-8, or not recognized at all.Īdditionally, if the implementation tests for valid JSON as I recommend, it will reject even the input that is indeed encoded as UTF-8, because it doesn't start with an ASCII character UTF-16BE has only one NUL in the first four bytes, so it won't be recognized.UTF-32LE the first byte is not followed by three NULs, so it won't be recognized.UTF-32BE doesn't start with three NULs, so it won't be recognized.Now, if the file starts with BOM it will look like this: 00 00 FE FF - UTF-32BE Not only it is illegal in JSON and not needed, it actually breaks all software that determine the encoding using the method presented in RFC 4627:ĭetermining the encoding and endianness of JSON, examining the first four bytes for the NUL byte: 00 00 00 xx - UTF-32BE Not only it is illegal in JSON, it is also not needed to determine the character encoding because there are more reliable ways to unambiguously determine both the character encoding and endianness used in any JSON stream (see this answer for details). Implementations MUST NOT add a byte order mark to the beginning of a JSON text. Additionally, a byte order mark is not necessary in UTF-8,Īs that encoding does not have endianness issues it serves only to Some authorities recommendĪgainst using the byte order mark in POSIX (Unix-like) scripts,įor this reason and for wider interoperability and philosophicalĬoncerns. The script interpreter from being executed. Presence of the BOM (0圎F 0xBB 0xBF) before the shebang will prevent "exec" function specifically detects the bytes 0x23 and 0x21, then the UTF-8 files may begin with the optional byte order mark (BOM) if the Scripts and other text files on current Unix-like systems. The shebang characters are represented by the same two bytes inĮxtended ASCII encodings, including UTF-8, which is commonly used for ![]() ![]() See Wikipedia, article: Shebang, section: Magic number: If you put something (like a BOM) before those characters, then the file will look like it had a different magic number and that can lead to problems. They are in fact a magic number that happens to be composed out of two ASCII characters. But actually the "#!" characters are not just characters. ![]() If the script is encoded in UTF-8, one may be tempted to include a BOM at the beginning. It tells the system which interpreter needs to be run when invoking such a script. Shell scripts, Perl scripts, Python scripts, Ruby scripts, Node.js scripts or any other executable that needs to be run by an interpreter - all start with a shebang line which looks like one of those: #!/bin/sh Here are examples of the BOM usage that actually cause real problems and yet many people don't know about it. ![]()
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