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

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Robert Moss
Robert Moss on 9 Sep 2013
Edited: Jan on 20 Jul 2021 at 16:33
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?

Accepted Answer

Jan
Jan on 10 Sep 2013
Edited: Jan on 20 Jul 2021 at 16:33
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);
  6 Comments
Chris Eguires
Chris Eguires on 20 Jul 2021 at 16:18
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...

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More Answers (5)

Arthur
Arthur on 9 Sep 2013
exist('dirname','dir')
Returns 7 if the dir is on your path, 0 if not.
  3 Comments
Arthur
Arthur on 9 Sep 2013
Ah yes you're right. I thought it check if it's on the searchpath, but it doesn't.

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Sean de Wolski
Sean de Wolski on 9 Sep 2013
Edited: Sean de Wolski on 9 Sep 2013
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
  2 Comments

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Brett
Brett on 14 Jun 2016
Edited: Brett on 14 Jun 2016
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\".


Image Analyst
Image Analyst on 9 Sep 2013
Edited: Image Analyst on 9 Sep 2013
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.

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