What OS are you using?
A user can not modify a file with another user's permission. Only an admin, or user in the same group, would be able to modify that file.
To mitigate this issue first change the permission of the original file to the user running gulp. Or add the gulp user to that folder/file.

The options.mode only affects "folders that need to be created" not existing folders with another user's permissions.

Yeah, I understand how chmod works on GNU/Linux. But on my systems gulp can and will by run by many different users (which are in the same group, though). IMO gulp has absolutely no need to run chmod on this file, since he only needs to write to it.

If I'm unable to turn of this feature I'm absolute ok with catching and ignoring it - my only intention is that the watcher doesn't fail because of this. Could you show me an example how to catch this error?

@hashworks this shouldn't be a problem. can you go here in vinyl-fs (in your local node_modules folder) and add some logging and let me know what these vars are?

https://github.com/wearefractal/vinyl-fs/blob/96867b4687d3a4c09cdd4db9a49134a87543b683/lib/dest/writeContents/index.js#L48

My node_modules/gulp/node_modules/vinyl-fs/lib/dest/writeContents/index.js is different: http://pastebin.com/zr76Kt6q

However I added this before line 27:

console.log(currentMode);
console.log(file.stat.mode);

Which results in:

436
33188
[16:03:54] 'sass' errored after 15 ms
[16:03:54] Error: EPERM, chmod 'foobar.css'

It's different? Can you run npm ls vinyl-fs ?

└─┬ gulp@3.8.11
└─ vinyl-fs@0.3.13

Just as the package.json of gulp says - ^0.3.0.

Can you try this with gulp 4? AFAIK this should be totally fixed

Seems like the 4.0 build is broken:
`npm install --save-dev git://github.com/#4.0'

var gulp = require('gulp');

gulp.task('default', function() {
    return gulp.src('./screen.css')
        .pipe(gulp.dest('./'));
});

/usr/local/lib/node_modules/gulp/bin/gulp.js:129
    gulpInst.start.apply(gulpInst, toRun);
                   ^
TypeError: Cannot call method 'apply' of undefined
    at /usr/local/lib/node_modules/gulp/bin/gulp.js:129:20
    at process._tickDomainCallback (node.js:463:13)

This happens as well when I call a gulpfile.js that only includes var gulp = require('gulp');.

@hashworks you need to be using the version of the CLI globally installed from gulpjs/gulp-cli#4.0

Ah, that was obvious.

It works with 4.0, no chmod error. I'll wait for a release then. Thanks 👍

@hashworks There was a bug with the chmod stuff in 3.x - feel free to use the 4.0 stuff it's stable, just waiting on a few more issues to land before we publish