diff --git a/Makefile b/Makefile
index 742aea1..88d8490 100644
--- a/Makefile
+++ b/Makefile
@@ -1,3 +1,5 @@
-all: era_copy
+all: era_copy era_apply
 era_copy: era_copy.c
 	gcc -o era_copy -Wall era_copy.c
+era_apply: era_apply.c
+	gcc -o era_apply -Wall era_apply.c
diff --git a/era_apply.c b/era_apply.c
new file mode 100644
index 0000000..1871df7
--- /dev/null
+++ b/era_apply.c
@@ -0,0 +1,131 @@
+/**
+ * Applies `era_copy` output to a file or block device
+ *
+ * Author: Vitaliy Filippov <vitalif@yourcmc.ru>, 2019
+ * License: GNU GPLv3.0 or later
+ */
+
+#define _LARGEFILE64_SOURCE
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <unistd.h>
+#include <string.h>
+#include <stdlib.h>
+#include <stdio.h>
+
+#define XML_BUFSIZE 1024
+#define COPY_BUFSIZE 0x400000
+#define SIGNATURE "ERARANGE"
+
+static void* copy_buffer = NULL;
+
+void apply_blocks(int src, int dst, off64_t start, off64_t length)
+{
+	off64_t copied = 0;
+	ssize_t fact = 0, written = 0, fact_write = 0;
+	if (!copy_buffer)
+	{
+		copy_buffer = malloc(COPY_BUFSIZE);
+		if (!copy_buffer)
+		{
+			fprintf(stderr, "Failed to allocate %d bytes\n", COPY_BUFSIZE);
+			exit(1);
+		}
+	}
+	if (lseek64(dst, start, 0) < 0)
+	{
+		fprintf(stderr, "Failed to lseek in output file: %s\n", strerror(errno));
+		exit(1);
+	}
+	while (length > copied)
+	{
+		fact = read(src, copy_buffer, length-copied > COPY_BUFSIZE ? COPY_BUFSIZE : length-copied);
+		if (fact <= 0)
+		{
+			fprintf(stderr, "Read error: %s\n", strerror(errno));
+			exit(1);
+		}
+		written = 0;
+		while (written < fact)
+		{
+			fact_write = write(dst, copy_buffer, fact-written);
+			if (fact_write <= 0)
+			{
+				fprintf(stderr, "Write error: %s\n", strerror(errno));
+				exit(1);
+			}
+			written += fact_write;
+		}
+		copied += fact;
+	}
+}
+
+void read_era_copy_and_apply(int src, int dst)
+{
+	long long sign = 0, start = 0, length = 0;
+	int r;
+	while (1)
+	{
+		r = read(src, &sign, 8);
+		if (r == 0)
+		{
+			break;
+		}
+		if (r < 8 ||
+			read(src, &start, 8) < 8 ||
+			read(src, &length, 8) < 8)
+		{
+			if (errno)
+				fprintf(stderr, "read error: %s\n", strerror(errno));
+			else
+				fprintf(stderr, "premature end of file\n");
+			exit(1);
+		}
+		if (sign != *((long long*)SIGNATURE))
+		{
+			fprintf(stderr, "era_copy signature does not match\n");
+			exit(1);
+		}
+		apply_blocks(src, dst, start, length);
+	}
+}
+
+void era_apply(char *dst_path)
+{
+	struct stat sb;
+	int dst;
+	if (stat(dst_path, &sb) != 0)
+	{
+		fprintf(stderr, "Failed to stat %s: %s\n", dst_path, strerror(errno));
+		exit(1);
+	}
+	// prevent writing to mounted devices
+	dst = open(dst_path, ((sb.st_mode & S_IFBLK) ? O_EXCL : 0) | O_WRONLY | O_LARGEFILE);
+	if (dst < 0)
+	{
+		fprintf(stderr, "Failed to open %s for writing: %s\n", dst_path, strerror(errno));
+		exit(1);
+	}
+	read_era_copy_and_apply(0, dst);
+	// fsync and close
+	fsync(dst);
+	close(dst);
+}
+
+int main(int narg, char *args[])
+{
+	if (narg < 2)
+	{
+		fprintf(stderr,
+			"era_apply - applies era_copy output to a file or block device\n"
+			"(c) Vitaliy Filippov, 2019+, distributed under the terms of GNU GPLv3.0 or later license\n"
+			"\n"
+			"USAGE:\nera_apply DESTINATION < era_copy_output.bin\n"
+		);
+		exit(1);
+	}
+	era_apply(args[1]);
+	return 0;
+}
diff --git a/era_copy.c b/era_copy.c
index 2a4903e..26a6e06 100644
--- a/era_copy.c
+++ b/era_copy.c
@@ -21,6 +21,7 @@
 
 #define XML_BUFSIZE 1024
 #define MAX_COPY 0x10000000
+#define SIGNATURE "ERARANGE"
 
 void copy_blocks(int src, int dst, off64_t start, off64_t length)
 {
@@ -42,7 +43,6 @@ void copy_blocks(int src, int dst, off64_t start, off64_t length)
 void read_era_invalidate_and_copy(FILE *fp, int src, int era_block_size)
 {
 	// read input XML
-	char* signature = "ERARANGE";
 	char buf[XML_BUFSIZE] = { 0 };
 	char c = 0;
 	long long start = 0, length = 0;
@@ -72,8 +72,8 @@ void read_era_invalidate_and_copy(FILE *fp, int src, int era_block_size)
 		}
 		start = start*era_block_size;
 		length = length*era_block_size;
-		// write a very simple binary format: signature, start, length, data, ...
-		write(1, signature, 8);
+		// write a very simple binary format: SIGNATURE, start, length, data, ...
+		write(1, SIGNATURE, 8);
 		write(1, &start, 8);
 		write(1, &length, 8);
 		copy_blocks(src, 1, start, length);
@@ -103,11 +103,11 @@ int main(int narg, char *args[])
 	if (narg < 3)
 	{
 		fprintf(stderr,
-			"era_copy - parses era_invalidate output and copies specified blocks from one file/device to another\n"
+			"era_copy - parses era_invalidate output and saves changed blocks to a stream\n"
 			"(c) Vitaliy Filippov, 2019+, distributed under the terms of GNU GPLv3.0 or later license\n"
 			"\n"
 			"USAGE:\nera_invalidate --metadata-snapshot --written-since <ERA> <META_DEVICE> |\\\n"
-			"    era_copy <ERA_BLOCK_SIZE> <DATA_DEVICE>\n"
+			"    era_copy <ERA_BLOCK_SIZE> <DATA_DEVICE> > era_copy.bin\n"
 			"\n"
 			"ERA_BLOCK_SIZE is the block size you used when creating dm-era device\n"
 			"You can take it from `dmsetup table <DATA_DEVICE>`: it's the last number in the table\n"