diff --git a/usr.bin/comm/comm.c b/usr.bin/comm/comm.c
--- a/usr.bin/comm/comm.c
+++ b/usr.bin/comm/comm.c
@@ -129,12 +129,12 @@
 
 		/* if one file done, display the rest of the other file */
 		if (n1 < 0) {
-			if (n2 >= 0 && col2 != NULL)
+			if (n2 >= 0)
 				show(fp2, argv[1], col2, &line2, &line2len);
 			break;
 		}
 		if (n2 < 0) {
-			if (n1 >= 0 && col1 != NULL)
+			if (n1 >= 0)
 				show(fp1, argv[0], col1, &line1, &line1len);
 			break;
 		}
@@ -206,10 +206,12 @@
 	ssize_t n;
 
 	do {
-		(void)printf("%s%s\n", offset, *bufp);
+		/* offset is NULL when draining fp, not printing */
+		if (offset != NULL)
+			(void)printf("%s%s\n", offset, *bufp);
 		if ((n = getline(bufp, buflenp, fp)) < 0)
 			break;
-		if (n > 0 && (*bufp)[n - 1] == '\n')
+		if (n > 0 && offset != NULL && (*bufp)[n - 1] == '\n')
 			(*bufp)[n - 1] = '\0';
 	} while (1);
 	if (ferror(fp))