How to have Matlab respect/remember symbolic links in path?

Hi,

I'm working on a piece of code that will be used by many people on different machines, and so I'm using relative directory paths to define the location of several necessary source files (i.e. hard coding directory paths will not work).

I am working on an OSX machine as well.

Lets say I have files in two main locations

/Volumes/WorkingDir/BaseDir          (BASEDIR)

and

/Volumes/WorkingDir/ExtraFilesDir

The problem I'm finding is that if the folder BaseDir is actually a symbolic link (not an alias) to another folder located in

BaseDir -> /Volumes/OtherDir

then when I make a call to:

/Volumes/WorkingDir/BaseDir/../ExtraFilesDir

Matlab reports that it cannot find "ExtraFilesDir" because it actually is looking for the folder in

/Volumes

When I want it to be looking in

/Volumes/WorkingDir

The OSX Terminal does not have this problem, it respects and holds symbolic links in the working directory, whereas it seems Matlab does not. Does anyone know a way to have Matlab respect Symbolic Links? I.e. have

BASEDIR/../   equal to    /Volumes/WorkingDir

I realize I could set the "WorkingDir" as the base directory and it would work too, but there is a compatibility issue that exists there (just trust me on that one, it could be done, but would be a hassle)

Summary: In essence, I can get matlab to correctly follow symbolic links but not properly back out of a symbolic link, and I would like to know if this is possible.

Thanks!

[Daniel Shub]

I am confused and cannot follow your directory structure. You have a directory /Volumes/OtherDir and a symbolic link /Volumes/WorkingDir/BaseDir which points to /Volumes/OtherDir. What I cannot figure out is where is ExtraFilesDir. I don't see how ExtraFilesDir could be accessible from /Volumes/WorkingDir/ unless ExtraFilesDir is located in /Volumes/OtherDir.

If this is the case then looking in /Volumes/OtherDir for ExtraFilesDir should work.

[Alexander]

So BaseDir is a folder that is a symbolic link that points towards the "OtherDir" folder.

That symbolic link is located in the "WorkingDir"

I would like Matlab to remember that the symbolic link is located in "WorkingDir" so that when I do (for example) "cd /Volumes/WorkingDir/BaseDir/.." I end up at Working Dir again.

If you do this in Matlab, you'll see that you end up at "/Volumes". Matlab doesn't remember that it used a symbolic link to get to BaseDir, so it moving up one level in the directory doesn't properly go back to WorkingDir.

[Alexander]

where the "/.." at the end denotes "go up one level in the directory".

"cd .." well move from "/A/B" to "/A" for example

[Daniel Shub]

I understand now. It appears that MATLAB only handles links physically and not logically. The problem is not /.., but rather the following of the symbolic link. For me

cd /Volumes/WorkingDir/BaseDir

pwd

returns

/Volumes/OtherDir

where /Volumes/WorkingDir/BaseDir -> /Volumes/OtherDir

I wonder if Jan's getfullpath would help

http://www.mathworks.com/matlabcentral/fileexchange/28249-getfullpath

Answer 1

[Walter Roberson]

I thought the behavior you noted is a bug, so I went looking for reference material to support your opinion. Instead I ended up finding support for the form used by MATLAB.

The appropriate POSIX routine to determine the current working directory is getcwd(), the official POSIX description of which starts,

The getcwd() function shall place an absolute pathname of the current working directory in the array pointed to by buf, and return buf. The pathname copied to the array shall contain no components that are symbolic links.

I not know why POSIX choose that behavior, but one cannot fault Mathworks with going with standard system calls rather than working through the paths step by step to figure out where one is in the symbolic tree.