Under Linux I can open a directory using opendir and then use readdir to get the filenames.
I have been experimenting with scandir and thought “great I can search for the files in this directory that I want by passing in a custom filter”, and sort using a custom sort where I want to sort by creation date. But then I realised how limited the dirent structure is. It contains only minimal information.
Is this the only API possible? i.e. do I have to stat every single file to get it’s size for sorting? Is this how ls -t works?
That is, indeed, how ls -t works, as ‘strace ls -t’ will confirm. Historically, a UNIX directory was just a special file containing a list of file names, and applications were expected to read and parse that “file” themselves. Naturally, that led to problems when newer file systems were developed that expanded the fixed length of file names, so the opendir/readdir/closedir interface was developed to abstract away the filesystem directory implementation. But the limitation on what is directly available in a directory listing remains.