diff --git a/include/villas/io.h b/include/villas/io.h
index 293ec9c20..51b9d95eb 100644
--- a/include/villas/io.h
+++ b/include/villas/io.h
@@ -40,8 +40,6 @@ struct io {
 	int flags;
 
 	struct {
-		int counter;			/**< Number of samples, read or written by this IO instance */
-
 		/** A format type can use this file handle or overwrite the
 		 * format::{open,close,eof,rewind} functions and the private
 		 * data in io::_vd.
@@ -75,6 +73,10 @@ int io_open(struct io *io, const char *uri);
 
 int io_close(struct io *io);
 
+void io_header(struct io *io);
+
+void io_footer(struct io *io);
+
 int io_print(struct io *io, struct sample *smps[], unsigned cnt);
 
 int io_scan(struct io *io, struct sample *smps[], unsigned cnt);
diff --git a/include/villas/io_format.h b/include/villas/io_format.h
index 599acd34c..5f8ecb14a 100644
--- a/include/villas/io_format.h
+++ b/include/villas/io_format.h
@@ -76,6 +76,13 @@ struct io_format {
 
 	int (*print)(struct io *io, struct sample *smps[], unsigned cnt);
 	int (*scan)( struct io *io, struct sample *smps[], unsigned cnt);
+
+	/** Print a header. */
+	void (*header)(struct io *io);
+
+	/** Print a footer. */
+	void (*footer)(struct io *io);
+
 	/** @} */
 
 	/** @{
diff --git a/lib/io.c b/lib/io.c
index 1f814185d..dfcdba997 100644
--- a/lib/io.c
+++ b/lib/io.c
@@ -218,16 +218,30 @@ int io_stream_fd(struct io *io)
 
 int io_open(struct io *io, const char *uri)
 {
-	return io->_vt->open
+	int ret;
+
+	ret = io->_vt->open
 		? io->_vt->open(io, uri)
 		: io_stream_open(io, uri);
+	if (ret)
+		return ret;
+
+	io_header(io);
+
+	return ret;
 }
 
 int io_close(struct io *io)
 {
-	return io->_vt->close
+	int ret;
+
+	io_footer(io);
+
+	ret = io->_vt->close
 		? io->_vt->close(io)
 	 	: io_stream_close(io);
+
+	return ret;
 }
 
 int io_flush(struct io *io)
@@ -258,6 +272,18 @@ int io_fd(struct io *io)
 		: io_stream_fd(io);
 }
 
+void io_header(struct io *io)
+{
+	if (io->_vt->header)
+		io->_vt->header(io);
+}
+
+void io_footer(struct io *io)
+{
+	if (io->_vt->footer)
+		io->_vt->footer(io);
+}
+
 int io_print(struct io *io, struct sample *smps[], unsigned cnt)
 {
 	int ret;
diff --git a/lib/io/csv.c b/lib/io/csv.c
index 51e633550..227b19a56 100644
--- a/lib/io/csv.c
+++ b/lib/io/csv.c
@@ -194,6 +194,15 @@ int csv_fscan(FILE *f, struct sample *smps[], unsigned cnt, int flags)
 	return i;
 }
 
+void csv_header(struct io *io)
+{
+	FILE *f = io->mode == IO_MODE_ADVIO
+			? io->output.stream.adv->file
+			: io->output.stream.std;
+
+	fprintf(f, "# secs%cnsecs%coffset%csequence%cdata[]\n", CSV_SEPARATOR, CSV_SEPARATOR, CSV_SEPARATOR, CSV_SEPARATOR);
+}
+
 static struct plugin p = {
 	.name = "csv",
 	.description = "Tabulator-separated values",
@@ -203,7 +212,8 @@ static struct plugin p = {
 		.fscan	= csv_fscan,
 		.sprint	= csv_sprint,
 		.sscan	= csv_sscan,
-		.size = 0
+		.header	= csv_header,
+		.size = 0,
 	}
 };
 
diff --git a/lib/io/villas_human.c b/lib/io/villas_human.c
index 367ab4ba5..c69fafa35 100644
--- a/lib/io/villas_human.c
+++ b/lib/io/villas_human.c
@@ -233,24 +233,13 @@ int villas_human_fprint(FILE *f, struct sample *smps[], unsigned cnt, int flags)
 	return i;
 }
 
-int villas_human_print(struct io *io, struct sample *smps[], unsigned cnt)
+void villas_human_header(struct io *io)
 {
-	struct villas_human *h = (struct villas_human *) io->_vd;
-
 	FILE *f = io->mode == IO_MODE_ADVIO
 			? io->output.stream.adv->file
 			: io->output.stream.std;
 
-	if (!h->header_written) {
-		fprintf(f, "# %-20s\t\t%s\n", "sec.nsec+offset", "data[]");
-
-		if (io->flags & IO_FLUSH)
-			io_flush(io);
-
-		h->header_written = true;
-	}
-
-	return villas_human_fprint(f, smps, cnt, io->flags);
+	fprintf(f, "# %-20s\t\t%s\n", "sec.nsec+offset", "data[]");
 }
 
 int villas_human_fscan(FILE *f, struct sample *smps[], unsigned cnt, int flags)
@@ -280,28 +269,18 @@ int villas_human_open(struct io *io, const char *uri)
 	return 0;
 }
 
-void villas_human_rewind(struct io *io)
-{
-	struct villas_human *h = (struct villas_human *) io->_vd;
-
-	h->header_written = false;
-
-	io_stream_rewind(io);
-}
-
 static struct plugin p = {
 	.name = "villas.human",
 	.description = "VILLAS human readable format",
 	.type = PLUGIN_TYPE_IO,
 	.io = {
 		.open	= villas_human_open,
-		.rewind	= villas_human_rewind,
-		.print	= villas_human_print,
 		.fprint	= villas_human_fprint,
 		.fscan	= villas_human_fscan,
 		.sprint	= villas_human_sprint,
 		.sscan	= villas_human_sscan,
-		.size	= sizeof(struct villas_human)
+		.header = villas_human_header,
+		.size	= sizeof(struct villas_human),
 	}
 };