4 ms·

> For example, if we rsync -a /source /target, we trust that the contents of /target will exactly match the contents of /source You might trust that, but you'd

by wtbob 10y ago

> For example, if we rsync -a /source /target, we trust that the contents of /target will exactly match the contents of /source You might trust that, but you'd be wrong: $ cd /tmp $ mkdir foo $ cd foo $ mkdir bar $ mkdir baz $ touch bar/quux $ rsync -a ./bar ./baz $ ls baz bar $ ls -R baz baz: bar baz/bar: quux You see, without a final '/' rsync will put the source into the target, rather than synchronising the source and the target. Also, if you really want a sync as opposed to just a full copy, you probably want to add --delete (which will delete files in the target which don't exist in the source. So you probably want rsync -a --delete source/ target/.

mjaniczek 10y ago
That would make for a great property-based test. It would be interesting to see the minimal counter-examples to widely-believed properties that don't hold (not just for rsync but for dfferent CLI tools). (See John Hughes, testing Dropbox with QuickCheck: https://vimeo.com/158002499 https://vimeo.com/158002499) EDIT: s/Jon/John/
zeveb 10y ago
Incidentally, given the directory structure above, here's a good way to calculate sha256 checksums over the files. It shells out rather than use the IRONCLAD package to calculate the checksums. (let ((src #P"/tmp/foo/bar/") (dst #P"/tmp/foo/baz/")) (flet ((sha256sum (path) "Return the SHA256 checksum of PATH as a string (which is good enough for our purposes here)." (first (split-sequence:split-sequence #\Space (uiop:run-program `("sha256sum" ,(namestring path)) :output :string))))) (loop for src-path in (directory (uiop:merge-pathnames* "**/*.*" src)) for dst-path = (uiop:merge-pathnames* (uiop:subpathp src-path src) dst) for file = (uiop:truename* dst-path) if file when (uiop:file-pathname-p file) do (unless (string= (sha256sum src-path) (sha256sum dst-path)) (warn "~a does not match ~a" dst-path src-path)) end else do (warn "~a not found" dst-path))))

by wtbob 10y ago

mjaniczek 10y ago

That would make for a great property-based test. It would be interesting to see the minimal counter-examples to widely-believed properties that don't hold (not just for rsync but for dfferent CLI tools). (See John Hughes, testing Dropbox with QuickCheck: https://vimeo.com/158002499 https://vimeo.com/158002499) EDIT: s/Jon/John/

zeveb 10y ago

Incidentally, given the directory structure above, here's a good way to calculate sha256 checksums over the files. It shells out rather than use the IRONCLAD package to calculate the checksums. (let ((src #P"/tmp/foo/bar/") (dst #P"/tmp/foo/baz/")) (flet ((sha256sum (path) "Return the SHA256 checksum of PATH as a string (which is good enough for our purposes here)." (first (split-sequence:split-sequence #\Space (uiop:run-program `("sha256sum" ,(namestring path)) :output :string))))) (loop for src-path in (directory (uiop:merge-pathnames* "**/*.*" src)) for dst-path = (uiop:merge-pathnames* (uiop:subpathp src-path src) dst) for file = (uiop:truename* dst-path) if file when (uiop:file-pathname-p file) do (unless (string= (sha256sum src-path) (sha256sum dst-path)) (warn "~a does not match ~a" dst-path src-path)) end else do (warn "~a not found" dst-path))))