Index: bin/dd/args.c
===================================================================
--- bin/dd/args.c
+++ bin/dd/args.c
@@ -320,6 +320,7 @@
 	{ "ascii",	C_ASCII,	C_EBCDIC,	e2a_POSIX },
 	{ "block",	C_BLOCK,	C_UNBLOCK,	NULL },
 	{ "ebcdic",	C_EBCDIC,	C_ASCII,	a2e_POSIX },
+	{ "fsync",	C_FSYNC,	0,		NULL },
 	{ "ibm",	C_EBCDIC,	C_ASCII,	a2ibm_POSIX },
 	{ "lcase",	C_LCASE,	C_UCASE,	NULL },
 	{ "noerror",	C_NOERROR,	0,		NULL },
Index: bin/dd/dd.h
===================================================================
--- bin/dd/dd.h
+++ bin/dd/dd.h
@@ -101,6 +101,7 @@
 #define	C_NOXFER	0x10000000
 #define	C_NOINFO	0x20000000
 #define	C_PROGRESS	0x40000000
+#define	C_FSYNC		0x80000000
 
 #define	C_PARITY	(C_PAREVEN | C_PARODD | C_PARNONE | C_PARSET)
 
Index: bin/dd/dd.1
===================================================================
--- bin/dd/dd.1
+++ bin/dd/dd.1
@@ -252,6 +252,10 @@
 and
 .No pre- Ns Bx 4.3 reno
 systems.
+.It Cm fsync
+Perform an
+.Xr fsync 2
+on the output file before closing it.
 .It Cm lcase
 Transform uppercase characters into lowercase characters.
 .It Cm pareven , parnone , parodd , parset
Index: bin/dd/dd.c
===================================================================
--- bin/dd/dd.c
+++ bin/dd/dd.c
@@ -164,6 +164,8 @@
 		errx(1, "files is not supported for non-tape devices");
 
 	cap_rights_set(&rights, CAP_FTRUNCATE, CAP_IOCTL, CAP_WRITE);
+	if (ddflags & C_FSYNC)
+		cap_rights_set(&rights, CAP_FSYNC);
 	if (out.name == NULL) {
 		/* No way to check for read access here. */
 		out.fd = STDOUT_FILENO;
@@ -505,6 +507,11 @@
 		if (ftruncate(out.fd, out.seek_offset) == -1)
 			err(1, "truncating %s", out.name);
 	}
+
+	if (ddflags & C_FSYNC) {
+		if (fsync(out.fd) == -1)
+			err(1, "fsyncing %s", out.name);
+	}
 }
 
 void