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Comment by 2OEH8eoCRo0 | Hacker News Reader

Why does Docker feel like it was designed by people with no Unix background?

I don't know if your comment was intended to imply that Docker was against the Unix philosophy in some way (a debatable point, but not really one I share), or if you mean that the tools don't follow a lot of common Unix convension.

When Docker was only a few years old, I did keep running into lots of small things which implied that the people developing docker in fact did NOT have a Unix (or even Linux) background. Things like source code files having the wrong type of newlines (or a mix of types), and forgetting to add a newline to the last line in a file. (A correct Unix text file has a newline at the end of _every_ line, even the last one.) There were of course more giveaways than this, I just remember the newline stuff irritating me the most.

Why is newline at the end relevant?

I remember not having a newline breaks some tools... but why? It can't be because of unix philosophy!?

Some old tools had bugs where they'd read a line (up to the new line) and then process it, so if the last line didn't end with a new line they'd never do the processing. So a manual workaround for bugs became the convention.

Back in ~2002 this was the case with cron. Found out the hard way when all the backup tapes we desperately needed were completely empty.

No, that is not a bug and there was never such a thing as "manually" adding a trailing newline. All tools add newlines automatically where they should be.

Unix has ALWAYS defined a line of text as being terminated by a newline. The last line in the file is not an exception.

so that you can cat(1) multiple files at once, and their bookends don't get glued.

Unix's first job in life was as a documentation processing system. It was made to be very good at dealing with text. All of the tools which process text expect every line to end in a newline. The last line is not exempt from this. All classic Unix text editors will automatically append a trailing newline to any text file you create with them. Some modern tools may be _tolerant_ of omitted trailing newlines, but you shouldn't rely on that. A text file should always have a newline as its last character. Otherwise, it's not _really_ a text file.

POSIX defines it more succinctly than I do: A text file contains one or more "lines" and every "line" is terminated by a "newline."

https://pubs.opengroup.org/onlinepubs/9699919799/basedefs/V1...

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