Given a file name, how can I programmatically distinguish between scripts and functions in MATLAB?
If I attempt to pass an argument to a script, I get Attempt to execute SCRIPT somescript as a function:. Is there a way to detect this without attempting to execute it?
Update: As @craq pointed out, shortly after this question was posted, there was an article about this on MATLAB Central: http://blogs.mathworks.com/loren/2013/08/26/what-kind-of-matlab-file-is-this/
Didn't find a clean solution, but you can probably use try-catch (as @Ilya suggested) and nargin
EDIT - Use function to avoid some naming conflict; use exist to further classify the input (e.g. MEX-file)
function is_script = is_a_script( varargin )
% is_a_script( varargin ) returns one of the following:
% 1: if the input is a script
% 0: if the input is a function
% -1: if the input is neither a function nor a script.
is_script = 0;
switch( exist(varargin{1}) )
case 2
% If the input is not a MEX or DLL or MDL or build-in or P-file or variable or class or folder,
% then exist() returns 2
try
nargin(varargin{1});
catch err
% If nargin throws an error and the error message does not match the specific one for script, then the input is neither script nor function.
if( strcmp( err.message, sprintf('%s is a script.',varargin{1}) ) )
is_script = 1;
else
is_script = -1;
end
end
case {3, 4, 5, 6} % MEX or DLL-file, MDL-file, Built-in, P-file
% I am not familiar with DLL-file/MDL-file/P-file. I assume they are all considered as functions.
is_script = 0;
otherwise % Variable, Folder, Class, or other cases
is_script = -1;
end
isFunction function, but inside that use this method rather than my very clumsy one.
does not know how to answer nargin/nargout, but that doesn't break your method. Also, why don't you compare err.identifier instead of err.message?catch statement: if I use, as the variable name, m_file_in_question.m, the strcmp will return False as the err.message will still be using the "short" name (without .m). Instead, look for a partial match, e.g. with strfind (but recognize that other error messages would generate "this is a function" return value, which is not actually what you want).mex question added to my answer above... feel free to use.
exist() can help further address some corner cases like a MEX file.If you are willing to use semi-documented features, here is something to try:
function tf = isfunction(fName)
t = mtree(fName, '-file');
tf = strcmp(t.root.kind, 'FUNCTION');
end
This is the same function used in MATLAB Cody and Contests to measure code length.
This is a bit of a hack, but... here is a function that will return true if the argument is a function, and false if it's not. It is possible that there are exceptions where this won't work - I look forward to comments.
EDIT - catching the case where the function is in a mex file...
function b = isFunction(fName)
% tries to determine whether the entity called 'fName'
% is a function or a script
% by looking at the file, and seeing if the first line starts with
% the key word "function"
try
w = which(fName);
% test for mex file:
mx = regexp(w, [mexext '$']);
if numel(mx)>0, b = true; return; end
% the correct thing to do... as shown by YYC
% if nargin(fName) >=0, b = true; return; end
% my original alternative:
fid = fopen(w,'r'); % open read only
while(~feof(fid))
l = fgetl(fid);
% strip everything after comment
f = strtok(l, '%');
g = strtok(f, ' ');
if strcmpi(g, 'function'), b=true; break; end
if strlen(g)>0, b=false; break; end
end
fclose(fid);
catch
fprintf(1, '%s not found!\n');
b = false;
end