Today’s Erlang Thursday is filelib:is_file/1.

filelib:is_file/1 takes a string representing a filename, and returns a true or false depending on if the name refers to a file or directory.

This can be useful if you are having to read from a configuration file and need to ensure that the file or directory exists before trying to process it, so that you can give a nice error message before quitting, instead of just causing a system error to be raised.

filelib:is_file("foo").
% false
filelib:is_file("junk").
% true
filelib:is_file("tmp").
% true
filelib:is_file("tempmp").
% false
filelib:is_file("temp").
% true
filelib:is_file("/usr/local/bin").
% true
filelib:is_file("/usr/local/var").
% true
filelib:is_file("/usr/local/vars").
% false
filelib:is_file(".").
% true
filelib:is_file("..").
% true

filelib:is_file/1 can also take a atom, or even a deeplist(), representing the filename as well.

filelib:is_file(foo).
% false
filelib:is_file(junk).
% true
filelib:is_file(["/usr", ['/local', '/bin']]).
% true

–Proctor