Linux Matlab - is it possible to determine whether a directory is a link?

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Art 2011-7-8

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I wrote a simple Matlab script using "dir" to recursively follow directories in a linux environment. The only thing is I don't want to follow linked directories. Does Matlab have a way of figuring out which directories are linked directories? On my Linux window, linked dirs show up as

/dir_x -> /home/some_directory_path/some_other_path/

rather than just /dir_x

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Answer 1

Lorenzo Luengo 2011-7-8

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Try somthing like

[a,b]=system('ls -l /tmp/myfile | cut -c 1')

if b is an 'l' (ell), then /tmp/myfile is a link, if it's a 'd' then it's a regular directory. There are some other special types like 's','p','b','c' but most common are 'd' and 'l'.

Another way can be

[a,b]=system('stat -c ''%F'' /tmp/DELETEME')

If 'b' says 'symbolic link' there you got it, if it says 'directory', it is a directory.

Just another tip. Beware of newlines that may be at the end of b. I usually get rid of them piping the output through an

tr -d '[\r\n]'

at the end of the command. strtrim function is also handy. Regards!

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Answer 2

Jan 2011-7-8

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I assume you need a Mex function, which calls stat and uses the non-Posix macro S_ISLNK. See: http://www.mitchr.me/SS/exampleCode/AUPG/fileData.c.html But it is not trivial to consider Unicode file names, see: Answers: Matlab string to wchar under linux and CSSM: 301249.

I cannot test this under linux - perhaps you need further headers:

#include "mex.h"
#include <sys\stat.h>
void mexFunction(int nlhs, mxArray *plhs[], 
                 int nrhs, const mxArray *prhs[])
{
  char *FileName;
  struct stat S;
    // Check number and type of arguments:
    if (nrhs != 1) {
      mexErrMsgTxt("*** FileIsLink[mex]: 1 input required.");
    }
    if (nlhs > 1) {
      mexErrMsgTxt("*** FileIsLink[mex]: 1 output allowed.");
    }
    // Type of input arguments:
    if (!mxIsChar(prhs[0])) {
      mexErrMsgTxt("*** FileIsLink[mex]: 1st input must be the file name.");
    }
    // Obtain FileName:
    if ((FileName = mxArrayToString(prhs[0])) == NULL) {
      mexErrMsgTxt("*** FileIsLink[mex]: "
                   "Cannot convert FileName to C-string.");
    }
    // Get the status and create output:
    if (stat(FileName, &S) == 0) {
      plhs[0] = mxCreateLogicalScalar((mxLogical) S_ISLNK(s.st_mode));
    } else {  // File not found:
      plhs[0] = mxCreateDoubleMatrix(0, 0, mxREAL);
    }
    mxFree(FileName);  
    return;
  }