Fix ensure_single_trailing_newline() on macs.

[drwells]

I'm not sure exactly why mac's version of sed produces different output here but it is easy enough to use something simpler. Just check if the last character is a newline: if not, then append a newline character.

[gassmoeller]

Nice simplification, but I feel like I dont understand why it has to be so complicated in the first place. Would my suggestion make it even simpler?

This would avoid using sed overall, which like you say behaves subtly different on Mac and Linux.

[drwells]

/rebuild

[gassmoeller]

👍

[drwells]

Actually - looking at this again, this change fixes the situation on macs where a file does not not end in \n but it doesn't prevent a case where a file ends in \n\n\n\n. I'll look into this later this week.

[gassmoeller]

Oh, I see, I didnt realize that was one of the purposes of this function as well. Then you probably have to keep the first sed command of the original (I think it came from here: https://stackoverflow.com/questions/7359527/removing-trailing-starting-newlines-with-sed-awk-tr-and-friends). Or was that the one that didnt work on Mac?

[drwells]

The case which didn't work on a mac was enforcing that files end in a newline (i.e., one instead of zero newlines) - this patch fixes that part.

[gassmoeller]

I think according to this answer the following should be pretty compatible and easy to understand:

# remove all trailing newlines and add exactly one newline instead
printf '%s\n' "$(cat "$file")" > "$file"

The command substitution into printf removes all potentially existing newlines at the end of the file, and printf adds exactly one newline because of the format given. Also works for file names with special characters and spaces. Couldnt test it on a Mac though.