- ISO 8601 is paywalled
- RFC allows a space instead of a T (e.g. 2020-12-09 16:09:…) which is nicer to read.
On the command line, space is what separates each argument. If a path contains a space, you either have to quote the entire path, or use an escape character (e.g. the \ character in most shells, the backtick in Powershell because Microsoft is weird, or the character’s hexadecimal value), otherwise the path will be passed to the command as separate arguments. For example, cat hello world.txt would try to print the files hello and world.txt.
It is a good practice to minimize the character set used by filenames, and best to only use English alphanumeric characters and certain symbols like -, _, and .. Non-printable characters (like the lower half of ASCII), weird diacritics (like ő or ű), ligatures, or any characters that could be misinterpreted by a program should be avoided.
This is why byte-safe encodings, like base64 or percent-encoding, are important. Transmitting data directly as text runs the risk of mangling the characters because some program misinterpreted them.
but what does the command line matter for dates? sure every once in a while you’ll have to pass a date as an argument on the command line but I think usually that kind of data is handled by APIs without human intervention, so once these are set up properly, I don’t see the problem
rsync -a "somedir" "somedir_backup_$(date)"
If the date command returns an RFC-3339-formatted string, the filename will contain a space. If, for example, you want to iterate over the files using for d in $(find...) and forget to set properly, it can cause issues.
Hm, I guess I just don’t agree that CLI usablity comes before readability.
But $(date) does return a string with spaces, at least on every system I’ve ever used. And what’s so bad about the possibility of spaces in filenames? They’re slightly inconvenient in a command line, but I haven’t used a commuter this century that didn’t support spaces in filenames.
Both arguments are surrounded by ", which should be space-safe.
At least in the shells I use, putting " makes spaces inside paths a non-issue.
