--- ray/src/util/radcompare.c	2020/07/09 17:29:04	2.25
+++ ray/src/util/radcompare.c	2020/07/27 16:49:56	2.26
@@ -1,5 +1,5 @@
 #ifndef lint
-static const char RCSid[] = "$Id: radcompare.c,v 2.25 2020/07/09 17:29:04 greg Exp $";
+static const char RCSid[] = "$Id: radcompare.c,v 2.26 2020/07/27 16:49:56 greg Exp $";
 #endif
 /*
  * Compare Radiance files for significant differences
@@ -35,6 +35,8 @@ double	max_lim = 0.25;		/* difference limit if non-neg
 
 int	lin1cnt=0, lin2cnt=0;	/* file line position */
 
+int	comment_c = '\0';	/* comment delimiter for text files */
+
 const char	nsuffix[10][3] = {		/* 1st, 2nd, 3rd, etc. */
 			"th","st","nd","rd","th","th","th","th","th","th"
 		};
@@ -111,7 +113,7 @@ usage()
 {
 	fputs("Usage: ", stderr);
 	fputs(progname, stderr);
-	fputs(" [-h][-s|-w|-v][-rel min_test][-rms epsilon][-max epsilon] reference test\n",
+	fputs(" [-h][-c#][-s|-w|-v][-rel min_test][-rms epsilon][-max epsilon] reference test\n",
 			stderr);
 	exit(2);
 }
@@ -149,6 +151,14 @@ read_line(LINEBUF *bp, FILE *fp)
 		if (!bp->str)
 			goto memerr;
 	}
+	if (comment_c) {		/* elide comment? */
+		char	*cp = sskip2(bp->str,0);
+		if (*cp == comment_c) {
+			*cp++ = '\n';
+			*cp = '\0';
+			bp->len = cp - bp->str;
+		}
+	}
 	return(bp->len);
 memerr:
 	fprintf(stderr,
@@ -557,7 +567,13 @@ compare_text()
 
 	if (report >= REP_VERBOSE) {
 		fputs(progname, stdout);
-		fputs(": comparing inputs as ASCII text\n", stdout);
+		fputs(": comparing inputs as ASCII text", stdout);
+		if (comment_c) {
+			fputs(", ignoring comments starting with '", stdout);
+			fputc(comment_c, stdout);
+			fputc('\'', stdout);
+		}
+		fputc('\n', stdout);
 	}
 	SET_FILE_TEXT(f1in);			/* originally set to binary */
 	SET_FILE_TEXT(f2in);
@@ -899,6 +915,9 @@ main(int argc, char *argv[])
 		switch (argv[a][1]) {
 		case 'h':			/* ignore header info. */
 			ign_header = !ign_header;
+			continue;
+		case 'c':			/* ignore comments */
+			comment_c = argv[a][2];
 			continue;
 		case 's':			/* silent operation */
 			report = REP_QUIET;