From d8b8e10ba48a4fc30db487ec05fb75efb79782bf Mon Sep 17 00:00:00 2001
From: Erik van der Kouwe <erik@minix3.org>
Date: Wed, 27 Jan 2010 07:48:06 +0000
Subject: [PATCH] Add notrunc conversion for dd tool

---
 commands/simple/dd.c | 13 ++++++++++---
 man/man1/dd.1        |  2 ++
 2 files changed, 12 insertions(+), 3 deletions(-)

diff --git a/commands/simple/dd.c b/commands/simple/dd.c
index 0f7874b86..dc6a9eca1 100644
--- a/commands/simple/dd.c
+++ b/commands/simple/dd.c
@@ -82,6 +82,7 @@ int num()
 #define NOERROR 0x0008
 #define SYNC 0x0010
 #define SILENT 0x0020
+#define NOTRUNC 0x0040
 #define BLANK ' '
 #define DEFAULT 512
 
@@ -142,7 +143,7 @@ char *argv[];
   void (*convert) ();
 #endif
   char *iptr;
-  int i, j;
+  int i, j, oflags;
 
   convert = null;
   argc--;
@@ -213,6 +214,10 @@ char *argv[];
 				convflag |= NOERROR;
 				continue;
 			}
+			if (is("notrunc")) {
+				convflag |= NOTRUNC;
+				continue;
+			}
 			if (is("sync")) {
 				convflag |= SYNC;
 				continue;
@@ -241,8 +246,10 @@ char *argv[];
 		(ifilename) ? ifilename : "stdin", strerror(errno));
 	exit(1);
   }
-  if ((ofd = ((ofilename) ? open(ofilename, seekseen ? O_WRONLY | O_CREAT
-					: O_WRONLY | O_CREAT | O_TRUNC, 0666)
+  oflags = O_WRONLY | O_CREAT;
+  if (!seekseen && (convflag & NOTRUNC) != NOTRUNC)
+  	oflags |= O_TRUNC;
+  if ((ofd = ((ofilename) ? open(ofilename, oflags, 0666)
 			: dup(1))) < 0) {
 	fprintf(stderr, "dd: Can't open %s: %s\n",
 		(ofilename) ? ofilename : "stdout", strerror(errno));
diff --git a/man/man1/dd.1 b/man/man1/dd.1
index 756ab0eb2..afdad2b8f 100644
--- a/man/man1/dd.1
+++ b/man/man1/dd.1
@@ -48,6 +48,8 @@ The options are:
 	\fBconv = swab\fR	\- Swap every pair of bytes
 .br
 	\fBconv = noerror\fR	\- Ignore errors and just keep going
+.br
+	\fBconv = notrunc\fR	\- Do not truncate unmodified blocks
 .br
 	\fBconv = silent\fR	\- Suppress statistics (MINIX 3 specific flag)
 .PP