Unless ivtfile has wildcard patterns recognized by your linux shell, use
dinfo = dir(ivtfile);
outdirs = {dinfo.folder};
ivtfilenames = fullfile(outdirs, {dinfo.name});
nfile = length(filenames)
ivtfilenames will be the fully-qualified file names. outdirs will be a cell array of folder names. You would typically only create a separate array to hold all of them if you had the case that the input ivtfile was a pattern that matched several directories, such as
ivtfile = 'ivt*/*.xlsx';
intending to match xlsx files in multiple folders each of which begins with "ivt"
