From 6e0b65303b01bb9669bf662364338ecf19e273a3 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?John=20Ankarstr=C3=B6m?= <john@ankarstrom.se>
Date: Wed, 14 Jul 2021 14:11:05 +0200
Subject: rtty.c: Don't eat output after repeated typed command

---
 Makefile |  4 ++--
 rtty.c   | 51 +++++++++++++++++++++++++++++++++++++--------------
 2 files changed, 39 insertions(+), 16 deletions(-)

diff --git a/Makefile b/Makefile
index 7197725..3720f8a 100644
--- a/Makefile
+++ b/Makefile
@@ -1,2 +1,2 @@
-install:
-	install ri rd /usr/local/bin
+install: rtty
+	install rd rtty /usr/local/bin
diff --git a/rtty.c b/rtty.c
index 42c9324..88ef214 100644
--- a/rtty.c
+++ b/rtty.c
@@ -27,38 +27,61 @@ main()
 	tv.tv_usec = 1;
 
 	for(;;){
-		/* Read from named pipe (out) and print on standard in. */
+		/*
+		 * User input is read from standard in and copied the
+		 * input pipe. It is saved in bufin for later use.
+		 */
+		FD_SET(0, &rfds0);
+		if(select(0+1, &rfds0, NULL, NULL, &tv) > 0){
+			nout = read(0, bufin, MAXBUF);
+			bufin[nout] = 0;
+			dprintf(fdin, "%s", bufin);
+			fflush(stdout);
+		}
+
+		/*
+		 * System output is read from the output pipe and copied
+		 * to standard out for the user to see.
+		 */
 		FD_SET(fdout, &rfds1);
 		if(select(fdout+1, &rfds1, NULL, NULL, &tv) > 0){
 			nout = read(fdout, bufout, MAXBUF);
 			if(!nout) continue;
 			bufout[nout] = 0;
 
-			/* Ignore repetition of typed command. */
-			for(bi = bufin, bo = bufout;;){
-				if(*bo == '\n')
+			/*
+			 * Bufin and bufout are copied to the temporary
+			 * pointers bi and bo. Bo is incremented in order
+			 * to skip any potential repetition of the command
+			 * given by the user on standard in. (It is assumed
+			 * that the typed command fits in bufin, i.e. is
+			 * not larger than MAXBUF.)
+			 */
+			bi = bufin;
+			bo = bufout;
+			for(;;){
+				if(*bo == '\n'){
+					bo++;
 					break;
+				}
 				if(*bo == 13){
 					bo++;
 					continue;
 				}
 				if(*bi != *bo){
-					printf("%s", bufout);
-					fflush(stdout);
+					bo = bufout;
 					break;
 				}
 				bi++; bo++;
 			}
-			bufin[0] = 0;
-		}
 
-		/* Read from standard in and print on named pipe (in). */
-		FD_SET(0, &rfds0);
-		if(select(0+1, &rfds0, NULL, NULL, &tv) > 0){
-			nout = read(0, bufin, MAXBUF);
-			bufin[nout] = 0;
-			dprintf(fdin, "%s", bufin);
+			/*
+			 * Bo is printed and bufin is cleared, so as not
+			 * to perform the skip again, incorrectly.
+			 */
+			printf("%s", bo);
 			fflush(stdout);
+			bufin[0] = 0;
 		}
 	}
 
-- 
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