Forgiveness is simpler than permission, and not subject to race conditions.
On Tue, Jun 5, 2012 at 8:01 AM, Tim Caswell <[email protected]> wrote: > As Ben and Bert say, if you checking for your own process and need to be > cross-platform, then the easiest and safest is to just try. > > function canWrite(path, callback) { > fs.open(path, function (err, fd) { > if (err) { > if (err.code === "EISDIR") { > // Create a file in the directory or something... > } > if (err.code === "EACCESS") { > return callback(null, false); > } > return callback(err); > } > fs.close(fd, function (err) { > if (err) return callback(err); > callback(null, true); > }); > }); > }); > > But the question is why do you need to know if you can write to it? Best to > just try to do whatever you're trying to do and watch for possible errors. > > > On Tue, Jun 5, 2012 at 9:49 AM, Bert Belder <[email protected]> wrote: >> >> On Jun 5, 4:31 pm, Tim Caswell <[email protected]> wrote: >> > Using the canWrite function from vfs-local, you can do it with a simple >> > stat.https://github.com/c9/vfs/blob/master/local/localfs.js#L19-23 >> > >> > function canWrite(owner, inGroup, mode) { >> > return owner && (mode & 00200) || // User is owner and owner can >> > write. >> > inGroup && (mode & 00020) || // User is in group and group can >> > write. >> > (mode & 00002); // Anyone can write. >> > >> > } >> > >> > Then in your code do: >> > >> > fs.stat(file, function (err, stat) { >> > if (err) { /* handle error */ } >> > if (canWrite(process.uid === stat.uid, process.gid === stat.gid, >> > stat.mode)) { >> > // you can write! >> > } >> > >> > }); >> > >> > I'm assuming you mean if the current owner can write. Things get more >> > complicated if you are running as root and want to see if some arbitrary >> > uid/gid can write because then you have to check for execute/search >> > access >> > in all the parent directories. In that case you would need something >> > likehttps://github.com/c9/vfs/blob/master/local/localfs.js#L104-124 >> >> I can think of a couple of other exceptions :-) >> - The directory resides on a read-only mount >> - You are using an operating system that uses ACLs like Windows or >> Solaris >> >> I don't think there's a generic solution to this problem. You should >> probably just try :-) >> >> -- >> Job Board: http://jobs.nodejs.org/ >> Posting guidelines: >> https://github.com/joyent/node/wiki/Mailing-List-Posting-Guidelines >> You received this message because you are subscribed to the Google >> Groups "nodejs" group. >> To post to this group, send email to [email protected] >> To unsubscribe from this group, send email to >> [email protected] >> For more options, visit this group at >> http://groups.google.com/group/nodejs?hl=en?hl=en > > > -- > Job Board: http://jobs.nodejs.org/ > Posting guidelines: > https://github.com/joyent/node/wiki/Mailing-List-Posting-Guidelines > You received this message because you are subscribed to the Google > Groups "nodejs" group. > To post to this group, send email to [email protected] > To unsubscribe from this group, send email to > [email protected] > For more options, visit this group at > http://groups.google.com/group/nodejs?hl=en?hl=en -- Job Board: http://jobs.nodejs.org/ Posting guidelines: https://github.com/joyent/node/wiki/Mailing-List-Posting-Guidelines You received this message because you are subscribed to the Google Groups "nodejs" group. To post to this group, send email to [email protected] To unsubscribe from this group, send email to [email protected] For more options, visit this group at http://groups.google.com/group/nodejs?hl=en?hl=en
