Are there any legitimate uses for newlines in filenames?
Unix is very permissive with filenames, and this can sometimes lead to a bunch of annoying corner cases when printing files. A well known example is when you put a newline in a filename, and it breaks naive parsing of a file list later in the pipeline.
There's not much mystery around why Unix decided to be permissive with filenames, so I'm not asking why newlines are allowed in filenames.
However, are there any situations where it is useful (or necessary, or desirable...) to have newlines in filenames? Hypothetical is okay, but "in the wild" would be even better.
I've only seen it when someone is deliberately trying to set up a trap (hacking, pranks) or by accident (programmer forgot to add a whitespace normalizer to their filename generator).
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Although this would be bad design for other reasons, I can imagine a situation where a field from one file or database can be used as a file name. Imagine something like
value="$(mysql -e 'select value from table')"
touch -- "$value"
This could then be used as some sort of misguided sanity check, or to re-populate the database or something like that. Yes, it's stretching it, but I can't really think of any reasonable reasons to have tabs, or backslashes or any special characters in filenames either, so if we consider some weird characters normal, why not newlines as well?
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I do this occasionally. It is sometimes useful to compare file titles where they aren't fixed lengths.
For example:
01 02
The Beatles The Rolling Stones
Help Satisfaction
.mp3 .flac
That can be the file name, or the first few lines of a file.
I don't use it terribly often.
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