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I have two arrays of objects: var a = [ {'id': 20}, {'id': 15}, {'id': 10}, {'id': 17}, {'id': 23} ]; var b = [ {'id': 90}, {'id': 15}, {'id': 17}, {'id': 23} ]; I'd like to get objects which are in a, but not in b. Results from this example would be: {'id': 20} and {'id': 10} . Because the arrays could be large, I need an efficient way to do this. // Make hashtable of ids in B var bIds = {} b.forEach(function(obj){ bIds[obj.id] = obj; }); // Return all elements in A, unless in B return a.filter(function(obj){ return !(obj.id in bIds); }); very minor addendum: If the lists are very large and

I am writing a simple Bash script to detect when a folder has been modified. It is something very close to: ls -lR $dir > a ls -lR $dir > b DIFF=$(diff a b) if [ $DIFF -ne 0 ] then echo "The directory was modified" Unfortunately, the if statement prints an error: [: -ne: unary operator expected I am not sure what is wrong with my script, would anyone please be able to help me? Thank you very much! Jary ls -lR $dir > a ls -lR $dir > b DIFF=$(diff a b) if [ "$DIFF" != "" ] then echo "The directory was modified" fi Paul Tomblin if ! diff -q a b &>/dev/null; then >&2 echo "different" fi tangens

Is there a quick and easy way to do such comparison? I've found few image compare questions from stackoverflow but none of those actually proved answer for this question. I have images files in my filesystem and a script that fetches images from urls. I want to check if the image in url is already the same that is on disk. Normally I would load the image in disk and url to a PIL object and use following function I found: def equal(im1, im2): return ImageChops.difference(im1, im2).getbbox() is None but this doesn't work if you have a image saved to disk with PIL as it gets compressed even if

I think i have a rather unique problem to solve. Well, i cant find enough information using Google. So here it goes, I work on a Java EE SOA application which stores XML documents as XML using Oracle XML DB. Whenever the XML changes, i increment the version and throw the previous version into a different table. The requirement now is, I should store the differences between 2 versions as XML, instead of the whole XML document. Is there any Java library which can do XML comparison? (XMLUnit, ... ?) Is there a standard XML Schema for capturing XML differences? What transformation technology can i

I inherited a project originally stored in CVS with all the revisions. I made quite a few edits, and I'm trying to compare all the changes I made in the original directory, in regards to new files added versus the old ones. Is there some sort of utility for hg/git where I can do a tree diff, or something of that nature? So that say, there's a mark between newly added files, deleted files, am I asking for too much? git diff does exactly that. but it only works for git projects. hg diff , svn diff pretty every version control system can diff directory trees To simply create a diff patch in git's

I'm going through a codebase and fixing whitespace oddities and generally correcting indentation and such things, and I want to make sure I haven't inadvertently made any other changes, so I'm doing git diff -w to display differences in all changed files while ignoring whitespace differences. The problem is that this is not actually ignoring all whitespace differences—at least what I consider to be merely whitespace differences. For instance, in the following output from git diff -w , -"Links": -{ - - "Thermal": - -{ - + "Links": { + "Thermal": { you can see that I've only removed superfluous

Are there any command line utilities that can be used to find if two JSON files are identical with invariance to within-dictionary-key and within-list-element ordering? Could this be done with jq or some other equivalent tool? Examples: These two JSON files are identical A : { "People": ["John", "Bryan"], "City": "Boston", "State": "MA" } B : { "People": ["Bryan", "John"], "State": "MA", "City": "Boston" } but these two JSON files are different: A : { "People": ["John", "Bryan", "Carla"], "City": "Boston", "State": "MA" } C : { "People": ["Bryan", "John"], "State": "MA", "City": "Boston" }

How can you determine all the files that changed in a given changeset? I'm not looking for a diff in this case, just a list of add/remove/modifications. hg log -vprX does a list of diffs but I just want the files. If you want to list only files that have changed then you should be using "status command" The following will list the changes to files in revision REV hg status --change REV Just remove p from your hg log -vpr will show the list of files. -p means show patch. You can also use a template to format the output to your taste. I know the question is for a single changeset, but if you'd