uniq(1): ignore trailing newlines when comparing lines

POSIX.1-2008 tweaked the uniq definition in light of AGI 1003.1-2001
#133.  uniq must now *ignore* the trailing newline when comparing
lines from the input.

In practice this means that if the last line in the input is missing a
trailing newline it isn't necessarily different from the line
preceding it.

So, uniq(1) now stubs the trailing newline before doing any line
comparisons.

For sake of simplicity, this patch introduces a second change: if the
last line in the input is missing a trailing newline and we choose to
print the line, a newline is appended when we print it.

Adopting the newline change aligns our implementation with with
POSIX.1-2008 (which we already claim in the manpage).  Adopting both
changes aligns our behavior with that of FreeBSD and GNU uniq.  For
better or worse, OpenBSD's uniq no longer behaves like NetBSD's uniq
in this corner case.

References:

POSIX.1-2001 uniq:
https://pubs.opengroup.org/onlinepubs/009695399/utilities/uniq.html

Austin Group Interpretation 1003.1-2001 #133:
https://collaboration.opengroup.org/austin/interps/documents/14355/AI-133.txt

POSIX.1-2008 uniq:
https://pubs.opengroup.org/onlinepubs/9699919799/utilities/uniq.html

--

Discussed with millert@.  With input from schwarze@.  Positive feedback
from bcallah@.

Thread: https://marc.info/?l=openbsd-tech&m=163581613829524&w=2

ok millert@

1 files changed, 11 insertions, 5 deletions

diff --git a/usr.bin/uniq/uniq.c b/usr.bin/uniq/uniq.c
index 67698f04399..7356d922390 100644
--- a/usr.bin/uniq/uniq.c
+++ b/usr.bin/uniq/uniq.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: uniq.c,v 1.28 2021/11/01 23:20:35 cheloha Exp $	*/
+/*	$OpenBSD: uniq.c,v 1.29 2021/11/17 23:09:38 cheloha Exp $	*/
 /*	$NetBSD: uniq.c,v 1.7 1995/08/31 22:03:48 jtc Exp $	*/
 
 /*
@@ -60,6 +60,7 @@ main(int argc, char *argv[])
 	char *prevline, *t1, *t2, *thisline;
 	FILE *ifp = NULL, *ofp = NULL;
 	size_t prevsize, thissize, tmpsize;
+	ssize_t len;
 	int ch;
 
 	setlocale(LC_CTYPE, "");
@@ -133,16 +134,21 @@ main(int argc, char *argv[])
 
 	prevsize = 0;
 	prevline = NULL;
-	if (getline(&prevline, &prevsize, ifp) == -1) {
+	if ((len = getline(&prevline, &prevsize, ifp)) == -1) {
 		free(prevline);
 		if (ferror(ifp))
 			err(1, "getline");
 		exit(0);
 	}
+	if (prevline[len - 1] == '\n')
+		prevline[len - 1] = '\0';
 	
 	thissize = 0;
 	thisline = NULL;
-	while (getline(&thisline, &thissize, ifp) != -1) {
+	while ((len = getline(&thisline, &thissize, ifp)) != -1) {
+		if (thisline[len - 1] == '\n')
+			thisline[len - 1] = '\0';
+
 		/* If requested get the chosen fields + character offsets. */
 		if (numfields || numchars) {
 			t1 = skip(thisline);
@@ -185,9 +191,9 @@ show(FILE *ofp, char *str)
 {
 	if ((dflag && repeats) || (uflag && !repeats)) {
 		if (cflag)
-			(void)fprintf(ofp, "%4d %s", repeats + 1, str);
+			fprintf(ofp, "%4d %s\n", repeats + 1, str);
 		else
-			(void)fprintf(ofp, "%s", str);
+			fprintf(ofp, "%s\n", str);
 	}
 }