Motivation
Not having newlines at the ends of files messes up lots of command line operations such as wc, >>, git and cat.
POSIX definition of a line:
3.206 Line A sequence of zero or more non- <newline> characters plus a terminating <newline> character.
| source: | http://pubs.opengroup.org/onlinepubs/9699919799/basedefs/V1_chap03.html#tag_03_206 |
|---|---|
| more: | http://stackoverflow.com/questions/729692/why-should-text-files-end-with-a-newline |
Examples
Example 1:
Given two files 1.txt and 2.txt without newlines at the end:
$ cat 1.txt 2.txt onetwo
The same two files with newlines:
$ cat 1.txt 2.txt one two
Example 2:
Appending to the end of a file doesn't work properly without a newline:
$ cat .gitignore *.pyc $ echo "*~" >> .gitignore $ cat .gitignore *.pyc*~
Example 3:
Word count (wc) doesn't correctly count lines:
$ cat missing.txt | wc -l 0
Commands
Finding missing newlines
Recursively find files missing trailing newlines in directory:
find . -type f -print0 | xargs -0 -L1 bash -c 'test "$(tail -c 1 "$0")" && echo "No new line at end of $0"'
Find files missing trailing newlines in a git repo:
git ls-files -z | xargs -0 -L1 bash -c 'test "$(tail -c 1 "$0")" && echo "No new line at end of $0"'
Adding missing newlines
Using your editor of choice, go to the last line and add newline
Ed:
ed -s file <<< w
Sed:
sed -i -e '$a\' file