You’re still doing unnecessary work. You’re turning a list of files into a string, then parsing the string back into words.
Your shell already provides a nice abstraction over calling readdir directly. A glob gives you a list, with no intermediate stage as a string that needs to be parsed. You can iterate directly over that list.
Every language provides either direct access to the C library, so that you can call readdir, or it provides some abstraction over it to make the process less annoying. In Common Lisp the function `directory` takes a pathname and returns a list of pathnames for the files in the named directory. In Rust there is the `std::fs::read_dir` that gives you an iterator that yields `io::Result<std::fs::DirEntry>`, allowing easy handling of io errors and also neatly avoiding an extra allocation. Raku has a function `dir` that returns a similar iterator, but with the added feature that it can match the names against a regex for you and only yield the matches. You can fill in more examples from your favorite languages if you want.
There is a glob() function you can use in POSIX C also to get an array of strings.
The getdents system call being used in the above program is the basis for implementing readdir.
It doesn't return a string, but rather a buffer of multiple directory entries.
The program isn't parsing a giant string; it is parsing out the directory entry structures, which are variable length and have a length field so the next one can be found.
The program writes each name including the null terminator, so that the output is suitable for utilities which understand that.
The problem is the phrase “suitable for shell pipelines”. If you are in a shell, you should not be doing anything like this. You should use a glob directly in the shell. You should not be calling an external program, having that program print out something, and then parsing it. Just use a glob right there in your shell script. If you do anything else, you are doing it wrong.
Your shell already provides a nice abstraction over calling readdir directly. A glob gives you a list, with no intermediate stage as a string that needs to be parsed. You can iterate directly over that list.
Every language provides either direct access to the C library, so that you can call readdir, or it provides some abstraction over it to make the process less annoying. In Common Lisp the function `directory` takes a pathname and returns a list of pathnames for the files in the named directory. In Rust there is the `std::fs::read_dir` that gives you an iterator that yields `io::Result<std::fs::DirEntry>`, allowing easy handling of io errors and also neatly avoiding an extra allocation. Raku has a function `dir` that returns a similar iterator, but with the added feature that it can match the names against a regex for you and only yield the matches. You can fill in more examples from your favorite languages if you want.