endnl () { [[ -f "$1" && -s "$1" && -z $(tail -c 1 "$1") ]]; }

Function to check whether a regular file ends with a newline

tail -c 1 "$1" returns the last byte in the file. Command substitution deletes any trailing newlines, so if the file ended in a newline $(tail -c 1 "$1") is now empty, and the -z test succeeds. However, $a will also be empty for an empty file, so we add -s "$1" to check that the file has a size greater than zero. Finally, -f "$1" checks that the file is a regular file -- not a directory or a socket, etc.
Sample Output
$ echo -n 'test' > /tmp/test1; if endnl /tmp/test1; then echo 'Ends in newline'; fi
$ echo 'test' > /tmp/test2; if endnl /tmp/test2; then echo 'Ends in newline'; fi
Ends in newline
$ echo -n '' > /tmp/test3; if endnl /tmp/test3; then echo 'Ends in newline'; fi
$ echo '' > /tmp/test4; if endnl /tmp/test4; then echo 'Ends in newline'; fi
Ends in newline
$ cd /tmp; ls -lt | head -n 5
total 32768
-rw-r--r-- 1 nick nick    1 2010-08-25 12:22:23 test4
-rw-r--r-- 1 nick nick    0 2010-08-25 12:22:12 test3
-rw-r--r-- 1 nick nick    5 2010-08-25 12:21:52 test2
-rw-r--r-- 1 nick nick    4 2010-08-25 12:21:32 test1

By: quintic
2010-08-25 12:06:10

1 Alternatives + Submit Alt

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