Something to try when you get a message like this caused by a filename with a leading hyphen: “mv: illegal option -- u”
Published on 3rd December 2024 Estimated Reading Time: 2 minutesRecently, I downloaded some WEBP files from Ideogram and attempted to move them to another folder. That is when I got the message that you see in the title of this entry. Because I had not looked at the filenames, I baffled when I got this from a simple command that I had been using with some success until then. Because I was using an iMac, I tried the suggestion of installing coreutils to get GNU mv and cp to see if that would help:
brew install coreutils
The above command gave me gmv and gcp for the GNU versions of mv and cp that comes with macOS. Trying gmv only got me the following message:
gmv: cannot combine --backup with --exchange, -n, or --update=none-fail
The ls command could list all files, but not the WEBP ones. Thus, I executed the following to show what I wanted:
ls | grep -i webp
That got around the problem by doing a subset of the directory listing. It was then that I spotted the leading hyphen. To avoid the problem tripping me up again, I renamed the offending file using this command:
mv -- -iunS9U4RFevWpaju6ArIQ.webp iunS9U4RFevWpaju6ArIQ.webp
Here, the -- switch tells the mv command not to look for any more options and only to expect filenames. When I tried enclosing the filename in quotes, I still got problems, even that might have because I was using double quotes instead of single quotes. Another option is to escape the leading hyphen like this:
mv ./-iunS9U4RFevWpaju6ArIQ.webp iunS9U4RFevWpaju6ArIQ.webp
Once the offending file was renamed, I could move the files to their final location. That could have used the -- option too, saving me an extra command, only for my wanting this not to trip me up again. Naturally, working in Finder might have avoided all this as much as not having a file with a leading hyphen in its name, but there would have been nothing to learn then.