Today I Learned

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Is This A Directory Or A File -- ReasonML

When compiling ReasonML natively, we have access to a variety of additional modules including the Unix module. We can interact with directories and files using functions on Unix.

let current_dir = Unix.opendir(Unix.getcwd());
let first_file = Unix.readdir(current_dir);
/* is first_file a directory or a file? */
Unix.closedir(current_dir);

Here we open the current working directory, grab the first thing out of that directory — maybe it’s a file, maybe it’s a directory, maybe it is something else. Lastly, we close the directory.

let current_dir = Unix.opendir(Unix.getcwd());
let first_file = Unix.readdir(current_dir);

switch(Unix.stat(first_file)) {
| Unix.stats({ st_kind: Unix.S_REG }) => print_endline("Regular File")
| Unix.stats({ st_kind: Unix.S_DIR }) => print_endline("Directory")
| Unix.stats({ st_kind: Unix.S_LINK }) => print_endline("Link")
| Unix.stats({ st_kind: Unix.S_SOCK }) => print_endline("Socket")
| _ => print_endline("Something else")
};

Unix.closedir(current_dir);

There are a variety of kinds of files to switch on. Here, we are switching on Regular Files, Directories, Links, and Sockets. Everything else falls through.

See the Unix module docs for more details.