EPERM error when running Gulp as non-root - node.js

Question

I'm using Gulp to compile some assets on a simple standalone WordPress theme project.
When I run my gulp task that compiles some LESS files I get the following error:
stream.js:94
throw er; // Unhandled stream error in pipe.
^
Error: EPERM, chmod '/Users/harryg/Sites/sites/wordpress/wp-content/themes/samarkand-2/assets/css/main.min.css'
When I run it as sudo the task executes without problem.
Thinking it was a permissions error I chmod'd the entire theme folder and its contents to 777 but this doesn't solve the problem. I have gulp installed globally which may be the issue but I'm not sure how to solve.
EDIT
Even if I run the local gulp I get the same error. I.e. running node_modules/.bin/gulp from my project folder produces the same EPERM error.

Answer 1

`sudo chown -R `whoami` sites/wordpress/wp-content/themes/samarkand-2`
should fix it. Or whatever directory you want to start from. This is no dangerous and might come because of you node-installation. It's pretty common and should be fixed in general after running installs with npm#3.X.X

Answer 2

While #cwelske gives a "hacky" workaround in his answer, the link he provides to the bug report provides a nicer fix for Gulp 3: use vinyl-fs.
npm install vinyl-fs --save-dev
Modify your gulpfile to use VFS:
Add to your requires block: var vfs = require('vinyl-fs');
Modify your output pipe: .pipe(vfs.dest('./output'));
The reason I was facing this error is because the files were owned by a more generic group and user so that multiple team members could work on the project together. Obviously Ubuntu doesn't allow you to chmod someone else's files. I suspect the OP is in a similar situation (the web-server might own the files).
If you do not require this kind of setup, your other option is to change the files to be owned by your user, something like:
sudo chown -R me:me .
Setting file permissions to 777 are not going to help you, because unless you own the file, you cannot chmod it without sudo. (Hence it works when you run gulp as sudo.)

Answer 3

gulp 3.x has a bug that makes it want to chown all files regardless if it already has all required permissions or not. It is supposedly fixed in gulp 4.
The linked bug contains a nice workaround if you know that the files have the correct permissions: Simply replace fs.chmod with an empty function in your gulpfile.js:
var fs = require('fs');
if (1) fs.chmod = function (a, b, cb) {
cb(0);
}