diff --git a/tests/run_tests b/tests/run_tests
index 87d43fa..b2347d4 100755
--- a/tests/run_tests
+++ b/tests/run_tests
@@ -18,6 +18,7 @@ if ! [ -e /root/.ssh/id_rsa ]; then
     ssh -oStrictHostKeyChecking=no localhost true || exit 1
 fi
 
+umount /tmp/ZfsCheck*
 
 coverage run --branch --source zfs_autobackup -m unittest discover -vvvvf $SCRIPTDIR $@ 2>&1
 EXIT=$?
diff --git a/tests/test_zfscheck.py b/tests/test_zfscheck.py
index 4f75b59..8a24973 100644
--- a/tests/test_zfscheck.py
+++ b/tests/test_zfscheck.py
@@ -181,7 +181,7 @@ whole_whole2_partial	0	309ffffba2e1977d12f3b7469971f30d28b94bd8
         #breaks pipe when grep exists:
         #important to use --debug, since that generates extra output which would be problematic if we didnt do correct SIGPIPE handling
         shelltest("python -m zfs_autobackup.ZfsCheck test_source1@test --debug | grep -m1 'Hashing tree'")
-        time.sleep(1)
+        # time.sleep(5)
 
         #should NOT be mounted anymore if cleanup went ok:
         self.assertNotRegex(shelltest("mount"), "test_source1@test")
@@ -194,11 +194,11 @@ whole_whole2_partial	0	309ffffba2e1977d12f3b7469971f30d28b94bd8
 
         #breaks pipe when grep exists:
         #important to use --debug, since that generates extra output which would be problematic if we didnt do correct SIGPIPE handling
-        shelltest("python -m zfs_autobackup.ZfsCheck test_source1/vol@test --debug | grep -m1 'Hashing dev'")
-        time.sleep(1)
+        shelltest("python -m zfs_autobackup.ZfsCheck test_source1/vol@test --debug | grep -m1 'Hashing file'")
+        # time.sleep(1)
 
         r = shelltest("zfs list -H -o name -r -t all " + TEST_POOLS)
-        self.assertMultiLineEqual(r, """
+        self.assertMultiLineEqual("""
 test_source1
 test_source1/fs1
 test_source1/fs1/sub
@@ -210,7 +210,7 @@ test_source2/fs2/sub
 test_source2/fs3
 test_source2/fs3/sub
 test_target1
-""")
+""",r )
 
 
 
diff --git a/zfs_autobackup/BlockHasher.py b/zfs_autobackup/BlockHasher.py
index 3ea4252..0a37c90 100644
--- a/zfs_autobackup/BlockHasher.py
+++ b/zfs_autobackup/BlockHasher.py
@@ -70,11 +70,11 @@ class BlockHasher():
 
         with open(fname, "rb") as fh:
 
-            fsize = fh.seek(0, os.SEEK_END)
+            fh.seek(0, os.SEEK_END)
+            fsize=fh.tell()
             fh.seek(0)
 
             while fh.tell()<fsize:
-
                 chunk_nr=self._seek_next_chunk(fh, fsize)
                 if chunk_nr is False:
                     return
diff --git a/zfs_autobackup/ZfsCheck.py b/zfs_autobackup/ZfsCheck.py
index 1ba9875..1d7d81a 100644
--- a/zfs_autobackup/ZfsCheck.py
+++ b/zfs_autobackup/ZfsCheck.py
@@ -3,6 +3,7 @@ from __future__ import print_function
 import time
 from signal import signal, SIGPIPE
 
+from . import util
 from .TreeHasher import TreeHasher
 from .BlockHasher import BlockHasher
 from .ZfsNode import ZfsNode
@@ -63,38 +64,23 @@ class ZfsCheck(CliBase):
 
         return args
 
-    def generate_zfs_filesystem(self, snapshot, input_generator):
-        """ recursively hash all files in this snapshot, using block_hash_tree()
+    def prepare_zfs_filesystem(self, snapshot):
 
-        :type snapshot: ZfsDataset.ZfsDataset
-        """
         mnt = "/tmp/" + tmp_name()
+        self.debug("Create temporary mount point {}".format(mnt))
+        self.node.run(["mkdir", mnt])
+        snapshot.mount(mnt)
+        return mnt
 
-        try:
-            self.debug("Create temporary mount point {}".format(mnt))
-            self.node.run(["mkdir", mnt])
-
-            snapshot.mount(mnt)
-
-            tree_hasher=TreeHasher(self.block_hasher)
-
-            self.debug("Hashing tree: {}".format(mnt))
-            if not self.args.test:
-                if input_generator:
-                    for i in tree_hasher.compare(mnt, input_generator):
-                        yield i
-                else:
-                    for i in tree_hasher.generate(mnt):
-                        yield i
-
-        finally:
-            snapshot.unmount()
-            self.debug("Cleaning up temporary mount point")
-            self.node.run(["rmdir", mnt], hide_errors=True, valid_exitcodes=[])
+    def cleanup_zfs_filesystem(self, snapshot):
+        mnt = "/tmp/" + tmp_name()
+        snapshot.unmount()
+        self.debug("Cleaning up temporary mount point")
+        self.node.run(["rmdir", mnt], hide_errors=True, valid_exitcodes=[])
 
     # NOTE: https://www.google.com/search?q=Mount+Path+Limit+freebsd
     # Freebsd has limitations regarding path length, so we have to clone it so the part stays sort
-    def activate_volume_snapshot(self, snapshot):
+    def prepare_zfs_volume(self, snapshot):
         """clone volume, waits and tries to findout /dev path to the volume, in a compatible way. (linux/freebsd/smartos)"""
 
         clone_name = get_tmp_clone_name(snapshot)
@@ -122,92 +108,45 @@ class ZfsCheck(CliBase):
 
         raise (Exception("Timeout while waiting for /dev entry to appear. (looking in: {})".format(locations)))
 
-    def deacitvate_volume_snapshot(self, snapshot):
+    def cleanup_zfs_volume(self, snapshot):
         """destroys temporary volume snapshot"""
         clone_name = get_tmp_clone_name(snapshot)
         clone = snapshot.zfs_node.get_dataset(clone_name)
         clone.destroy(deferred=True, verbose=False)
 
-    def generate_zfs_volume(self, snapshot, input_generator):
-        try:
-            dev=self.activate_volume_snapshot(snapshot)
-
-            self.debug("Hashing dev: {}".format(dev))
-            if not self.args.test:
-                if input_generator:
-                    for i in self.block_hasher.compare(dev, input_generator):
-                        yield i
-                else:
-                    for i in self.block_hasher.generate(dev):
-                        yield i
-
-        finally:
-            self.deacitvate_volume_snapshot(snapshot)
-
-    def generate_zfs_target(self, input_generator):
-        """specified arget is a ZFS snapshot"""
-
-        snapshot = self.node.get_dataset(self.args.target)
-        if not snapshot.exists:
-            raise Exception("Snapshot {} not found".format(snapshot))
-
-        if not snapshot.is_snapshot:
-            raise Exception("Dataset {} should be a snapshot".format(snapshot))
-
-        dataset_type = snapshot.parent.properties['type']
-
-        if dataset_type == 'volume':
-            return self.generate_zfs_volume(snapshot, input_generator)
-        elif dataset_type == 'filesystem':
-            return self.generate_zfs_filesystem(snapshot, input_generator)
-        else:
-            raise Exception("huh?")
-
-    def generate_path(self, input_generator=None):
+    def generate_tree_hashes(self, prepared_target):
 
         tree_hasher = TreeHasher(self.block_hasher)
+        self.debug("Hashing tree: {}".format(prepared_target))
+        for i in tree_hasher.generate(prepared_target):
+            yield i
 
-        self.debug("Hashing tree: {}".format(self.args.target))
-        if input_generator:
-            for i in tree_hasher.compare(self.args.target, input_generator):
-                yield i
-        else:
-            for i in tree_hasher.generate(self.args.target):
-                yield i
+    def generate_tree_compare(self, prepared_target, input_generator=None):
 
-    def generate_file(self, input_generator=None):
+        tree_hasher = TreeHasher(self.block_hasher)
+        self.debug("Comparing tree: {}".format(prepared_target))
+        for i in tree_hasher.compare(prepared_target, input_generator):
+            yield i
 
+    def generate_file_hashes(self, prepared_target):
 
-        self.debug("Hashing file: {}".format(self.args.target))
-        if input_generator:
-            for i in self.block_hasher.compare(self.args.target, input_generator):
-                yield i
-        else:
-            for i in self.block_hasher.generate(self.args.target):
-                yield i
+        self.debug("Hashing file: {}".format(prepared_target))
+        for i in self.block_hasher.generate(prepared_target):
+            yield i
 
-    def generate(self, input_generator=None):
-        """generate checksums or compare (and generate error messages)"""
+    def generate_file_compare(self, prepared_target, input_generator=None):
 
-        if '@' in self.args.target:
-            self.verbose("Target is a ZFS snapshot.".format(self.args.target))
-            return self.generate_zfs_target(input_generator)
-        elif os.path.isdir(self.args.target):
-            self.verbose("Target is a directory, checking recursively.".format(self.args.target))
-            return self.generate_path(input_generator)
-        elif os.path.exists(self.args.target):
-            self.verbose("Target is single file or blockdevice.".format(self.args.target))
-            return self.generate_file(input_generator)
-        else:
-            raise Exception("Cant open {} ".format(self.args.target))
+        self.debug("Comparing file: {}".format(prepared_target))
+        for i in self.block_hasher.compare(prepared_target, input_generator):
+            yield i
 
-    def input_parser(self, file_name):
-        """parse input lines and generate items to use in compare functions"""
+    def generate_input(self):
+        """parse input lines and yield items to use in compare functions"""
 
         if self.args.check is True:
             input_fh=sys.stdin
         else:
-            input_fh=open(file_name, 'r')
+            input_fh=open(self.args.check, 'r')
 
         last_progress_time = time.time()
         progress_checked = 0
@@ -236,52 +175,101 @@ class ZfsCheck(CliBase):
 
         self.verbose("Checked {} hashes (skipped {})".format(progress_checked, progress_skipped))
 
+    def print_hashes(self, hash_generator):
+        """prints hashes that are yielded by the specified hash_generator"""
+
+        last_progress_time = time.time()
+        progress_count = 0
+
+        for i in hash_generator:
+
+            if len(i) == 3:
+                print("{}\t{}\t{}".format(*i))
+            else:
+                print("{}\t{}".format(*i))
+            progress_count = progress_count + 1
+
+            if self.args.progress and time.time() - last_progress_time > 1:
+                last_progress_time = time.time()
+                self.progress("Generated {} hashes.".format(progress_count))
+
+            sys.stdout.flush()
+
+        self.verbose("Generated {} hashes.".format(progress_count))
+        self.clear_progress()
+
+        return 0
+
+    def print_errors(self, compare_generator):
+        """prints errors that are yielded by the specified compare_generator"""
+        errors = 0
+        for i in compare_generator:
+            errors = errors + 1
+
+            if len(i) == 4:
+                (file_name, chunk_nr, compare_hexdigest, actual_hexdigest) = i
+                print("{}: Chunk {} failed: {} {}".format(file_name, chunk_nr, compare_hexdigest, actual_hexdigest))
+            else:
+                (chunk_nr, compare_hexdigest, actual_hexdigest) = i
+                print("Chunk {} failed: {} {}".format(chunk_nr, compare_hexdigest, actual_hexdigest))
+
+            sys.stdout.flush()
+
+        self.verbose("Total errors: {}".format(errors))
+        self.clear_progress()
+
+        return errors
+
+    def prepare_target(self):
+
+        if "@" in self.args.target:
+            # zfs snapshot
+            snapshot=self.node.get_dataset(self.args.target)
+            dataset_type = snapshot.parent.properties['type']
+
+            if dataset_type == 'volume':
+                return self.prepare_zfs_volume(snapshot)
+            elif dataset_type == 'filesystem':
+                return self.prepare_zfs_filesystem(snapshot)
+            else:
+                raise Exception("Unknown dataset type")
+        return self.args.target
+
+    def cleanup_target(self):
+        if "@" in self.args.target:
+            # zfs snapshot
+            snapshot=self.node.get_dataset(self.args.target)
+            dataset_type = snapshot.parent.properties['type']
+
+            if dataset_type == 'volume':
+                self.cleanup_zfs_volume(snapshot)
+            elif dataset_type == 'filesystem':
+                self.cleanup_zfs_filesystem(snapshot)
+
     def run(self):
 
+        compare_generator=None
+        hash_generator=None
         try:
-            last_progress_time = time.time()
-            progress_count = 0
-
-            #run as generator
-            if self.args.check==None:
-                for i in self.generate(input_generator=None):
-
-                    if len(i)==3:
-                        print("{}\t{}\t{}".format(*i))
-                    else:
-                        print("{}\t{}".format(*i))
-                    progress_count=progress_count+1
-
-                    if self.args.progress and time.time()-last_progress_time>1:
-                        last_progress_time=time.time()
-                        self.progress("Generated {} hashes.".format(progress_count))
-
-                    sys.stdout.flush()
-
-                self.verbose("Generated {} hashes.".format(progress_count))
-                self.clear_progress()
-                return 0
+            prepared_target=self.prepare_target()
+            is_dir=os.path.isdir(prepared_target)
 
             #run as compare
+            if self.args.check is not None:
+                input_generator=self.generate_input()
+                if is_dir:
+                    compare_generator = self.generate_tree_compare(prepared_target, input_generator)
+                else:
+                    compare_generator=self.generate_file_compare(prepared_target, input_generator)
+                errors=self.print_errors(compare_generator)
+            #run as generator
             else:
-                errors=0
-                input_generator=self.input_parser(self.args.check)
-                for i in self.generate(input_generator):
-                        errors=errors+1
+                if is_dir:
+                    hash_generator = self.generate_tree_hashes(prepared_target)
+                else:
+                    hash_generator=self.generate_file_hashes(prepared_target)
 
-                        if len(i)==4:
-                            (file_name, chunk_nr, compare_hexdigest, actual_hexdigest)=i
-                            print("{}: Chunk {} failed: {} {}".format(file_name, chunk_nr, compare_hexdigest, actual_hexdigest))
-                        else:
-                            (chunk_nr, compare_hexdigest, actual_hexdigest) = i
-                            print("Chunk {} failed: {} {}".format(chunk_nr, compare_hexdigest, actual_hexdigest))
-
-                        sys.stdout.flush()
-
-                self.verbose("Total errors: {}".format(errors))
-
-                self.clear_progress()
-                return min(255,errors)
+                errors=self.print_hashes(hash_generator)
 
         except Exception as e:
             self.error("Exception: " + str(e))
@@ -292,12 +280,26 @@ class ZfsCheck(CliBase):
             self.error("Aborted")
             return 255
 
+        finally:
+            #important to call check_output so that cleanup still functions in case of a broken pipe:
+            # util.check_output()
+
+            #close generators, to make sure files are not in use anymore when cleaning up
+            if hash_generator is not None:
+                hash_generator.close()
+            if compare_generator is not None:
+                compare_generator.close()
+            self.cleanup_target()
+
+        return errors
+
+
 def cli():
     import sys
     signal(SIGPIPE, sigpipe_handler)
 
     sys.exit(ZfsCheck(sys.argv[1:], False).run())
 
-if __name__ == "__main__":
 
+if __name__ == "__main__":
     cli()
diff --git a/zfs_autobackup/test.py b/zfs_autobackup/test.py
index 6c1e39b..14b6bba 100644
--- a/zfs_autobackup/test.py
+++ b/zfs_autobackup/test.py
@@ -1,70 +1,129 @@
 import os.path
 import os
+import subprocess
+import sys
 import time
-from random import random
+from signal import signal, SIGPIPE
 
-with open('test.py', 'rb') as fh:
+import util
 
-    # fsize = fh.seek(10000, os.SEEK_END)
-    # print(fsize)
-
-    start=time.time()
-    for i in range(0,1000000):
-        # fh.seek(0, 0)
-        fsize=fh.seek(0, os.SEEK_END)
-        # fsize=fh.tell()
-        # os.path.getsize('test.py')
-    print(time.time()-start)
+signal(SIGPIPE, util.sigpipe_handler)
 
 
-    print(fh.tell())
+try:
+    print ("voor eerste")
+    raise Exception("eerstre")
+except Exception as e:
+    print ("voor tweede")
+    raise Exception("tweede")
+finally:
+    print ("JO")
 
-sys.exit(0)
+def generator():
+
+    try:
+        util.deb('in generator')
+        print ("TRIGGER SIGPIPE")
+        sys.stdout.flush()
+        util.deb('after trigger')
+
+        # if False:
+        yield ("bla")
+        # yield ("bla")
+
+    except GeneratorExit as e:
+        util.deb('GENEXIT '+str(e))
+        raise
+
+    except Exception as e:
+        util.deb('EXCEPT '+str(e))
+    finally:
+        util.deb('FINALLY')
+        print("nog iets")
+        sys.stdout.flush()
+        util.deb('after print in finally WOOP!')
 
 
+util.deb('START')
+g=generator()
+util.deb('after generator')
+for bla in g:
+    # print ("heb wat ontvangen")
+    util.deb('ontvangen van gen')
+    break
+    # raise Exception("moi")
 
-checked=1
-skipped=1
-coverage=0.1
+    pass
+raise Exception("moi")
 
-max_skip=0
+util.deb('after for')
 
-
-skipinarow=0
 while True:
-    total=checked+skipped
+    pass
 
-    skip=coverage<random()
-    if skip:
-        skipped = skipped + 1
-        print("S {:.2f}%".format(checked * 100 / total))
-
-        skipinarow = skipinarow+1
-        if skipinarow>max_skip:
-            max_skip=skipinarow
-    else:
-        skipinarow=0
-        checked=checked+1
-        print("C {:.2f}%".format(checked * 100 / total))
-
-    print(max_skip)
-
-skip=0
-while True:
-
-    total=checked+skipped
-    if skip>0:
-        skip=skip-1
-        skipped = skipped + 1
-        print("S {:.2f}%".format(checked * 100 / total))
-    else:
-        checked=checked+1
-        print("C {:.2f}%".format(checked * 100 / total))
-
-        #calc new skip
-        skip=skip+((1/coverage)-1)*(random()*2)
-        # print(skip)
-        if skip> max_skip:
-            max_skip=skip
-
-    print(max_skip)
+#
+# with open('test.py', 'rb') as fh:
+#
+#     # fsize = fh.seek(10000, os.SEEK_END)
+#     # print(fsize)
+#
+#     start=time.time()
+#     for i in range(0,1000000):
+#         # fh.seek(0, 0)
+#         fsize=fh.seek(0, os.SEEK_END)
+#         # fsize=fh.tell()
+#         # os.path.getsize('test.py')
+#     print(time.time()-start)
+#
+#
+#     print(fh.tell())
+#
+# sys.exit(0)
+#
+#
+#
+# checked=1
+# skipped=1
+# coverage=0.1
+#
+# max_skip=0
+#
+#
+# skipinarow=0
+# while True:
+#     total=checked+skipped
+#
+#     skip=coverage<random()
+#     if skip:
+#         skipped = skipped + 1
+#         print("S {:.2f}%".format(checked * 100 / total))
+#
+#         skipinarow = skipinarow+1
+#         if skipinarow>max_skip:
+#             max_skip=skipinarow
+#     else:
+#         skipinarow=0
+#         checked=checked+1
+#         print("C {:.2f}%".format(checked * 100 / total))
+#
+#     print(max_skip)
+#
+# skip=0
+# while True:
+#
+#     total=checked+skipped
+#     if skip>0:
+#         skip=skip-1
+#         skipped = skipped + 1
+#         print("S {:.2f}%".format(checked * 100 / total))
+#     else:
+#         checked=checked+1
+#         print("C {:.2f}%".format(checked * 100 / total))
+#
+#         #calc new skip
+#         skip=skip+((1/coverage)-1)*(random()*2)
+#         # print(skip)
+#         if skip> max_skip:
+#             max_skip=skip
+#
+#     print(max_skip)
diff --git a/zfs_autobackup/util.py b/zfs_autobackup/util.py
index 5c86041..4d774b3 100644
--- a/zfs_autobackup/util.py
+++ b/zfs_autobackup/util.py
@@ -19,7 +19,7 @@ import sys
 
 
 def tmp_name(suffix=""):
-    """create temporary name unique to this process and node"""
+    """create temporary name unique to this process and node. always retruns the same result during the same execution"""
 
     #we could use uuids but those are ugly and confusing
     name="{}-{}-{}".format(
@@ -48,3 +48,18 @@ def output_redir():
 def sigpipe_handler(sig, stack):
     #redir output so we dont get more SIGPIPES during cleanup. (which my try to write to stdout)
     output_redir()
+    deb('redir')
+
+# def check_output():
+#     """make sure stdout still functions. if its broken, this will trigger a SIGPIPE which will be handled by the sigpipe_handler."""
+#     try:
+#         print(" ")
+#         sys.stdout.flush()
+#     except Exception as e:
+#         pass
+
+# def deb(txt):
+#     with open('/tmp/debug.log', 'a') as fh:
+#         fh.write("DEB: "+txt+"\n")
+
+