How can I determine if a directory is on the MATLAB path programmatically?

I want to be able to programmatically determine if an arbitrary directory is on the MATLAB path. I want to do this because the publish command will complain if you give it a file name that is not on the path. Is there a clever way to determine if a directory is on the MATLAB path without having to parse the path myself?

Answer 1

[Jan]

pathCell = regexp(path, pathsep, 'split');
if ispc  % Windows is not case-sensitive
  onPath = any(strcmpi(Folder, pathCell));
else
  onPath = any(strcmp(Folder, pathCell));
end

[EDITED] A faster version - beside the faster strsplit since Matlab R2013a:

s       = pathsep;
pathStr = [s, path, s];
onPath  = contains(pathStr, [s, Folder, s], 'IgnoreCase', ispc);

[Robert Moss]

This is the answer that works for me. Specifically my issue is that the publish function, when called programmatically, fails if the input filename is not on the MATLAB path, regardless of whether or not the full file specification is given. I prefer a method like this, rather than a work-around. This occurs in publish because it uses which.

[Sean de Wolski]

@Robert, I still don't see why just adding the directory to the path wouldn't be the best option here...

[Robert Moss]

@Sean, In many cases that would probably be fine, but in my specific instance the file that I am publishing is an m file that is in a class subdirectory, and I don't think that type of subdirectory should actually be on the path. (The directory within which a class directory resides should be on the path, but not the class directory itself).

[Image Analyst]

Then use genpath() to get subfolders added to the path also:

addpath(genpath(theFolder));

[Sean de Wolski]

This is correct @Robert. So why not add the parent path blindly? This is what you're checking anyway right?

[Chris Eguires]

For slightly more speed, you can just use strsplit(path,pathsep). Shouldnt make a big difference, but if you have thousands of paths, maybe a fraction of a second...

Answer 2

[Arthur]

exist('dirname','dir')

Returns 7 if the dir is on your path, 0 if not.

[Matt J]

This assumes that dirname is not the full system path name. If it is a full path, 7 will always be returned, even if that directory is not on the MATLAB path.

[Thomas]

Not sure this is correct. It will return 7 if the directory exists and 0 if the directory does not..

I do not think it has to do with the directory being on the path or not.

[Arthur]

Ah yes you're right. I thought it check if it's on the searchpath, but it doesn't.

Answer 3

[Sean de Wolski]

Parsing the path isn't so bad!

This seems like a simple check:

if ispc
  % Windows is not case-sensitive
  onPath = ~isempty(strfind(lower(path),lower('H:\Documents\MATLAB;')))
else
  onPath = ~isempty(strfind(path,'H:\Documents\MATLAB;'))
end

Of course for your use-case it's not too much work to just add the folder in question to the path regardless, addpath takes care of redundancy:

addpath H:\documents\MATLAB
addpath H:\documents\MATLAB
addpath H:\documents\MATLAB
addpath H:\documents\MATLAB
addpath H:\documents\MATLAB
clc
path

[Jan]

Instead of relying on the semicolon as a separator, using the command pathsep is more flexible because it considers the OS-specific separator automatically:

onPath = ~isempty(strfind(path, ['H:\Documents\MATLAB', pathsep]))

[Sean de Wolski]

Good to learn!

Answer 4

[Brett]

This made the most sense to me...

ismember(some_path, strsplit(path, pathsep))

These days I'm more familiar with Python than Matlab, so I'm sorta doing the Matlab equivalent of something like "file in pathstr.split(';')". I assume that checking membership is cheaper than searching... this logic may not be true for Matlab cell arrays, I'm not sure. My next assumption was that strsplit should always be preferred if your pattern is a known constant expression (vs. using regex for simple splitting which is an expensive operation). This avoids all the pitfalls of string matching, like false positives of "C:\some_path" being accidentally found inside "C:\some_path\sub_path\subsub\".

Answer 5

[Azzi Abdelmalek]

isdir('your_folder_name')

[Adam Danz]

isdir() or the newer isfolder() returns true if the input is a directory whether it's on-path or not (for full paths).

Answer 6

[Image Analyst]

Why can't you just give it the full filename? Use

fullFileName = fullfile(folder, baseFilename);

I mean, you already have the folder because you were going to use that to try to figure out if it was on the search path. But instead of doing that, just construct the full filename like I showed you above.

Alternatively, just try to open the file and check if the file ID indicates it didn't find it.

fid = fopen(baseFileName); % Don't use folder or full file name.
if fid == -1 .... etc.