MATLAB: Is there a MATLAB function to check whether another application has a lock on a data file in MATLAB 7.8 (R2009a)

MATLAB

I am using an application external to MATLAB to write to a data file. I have written MATLAB code that loads this file and processes the data. I would like my MATLAB code to check to make sure that the data file is not open in the other application before loading the data.

Best Answer

You can use 'fileattrib' function to check whether you have the write access to a particular file. The attributes 'UserRead' and 'UserWrite' obtained by executing the command will indicate whether you have the read and write access to the file. Please note that the value '1' for a particular attribute indicates that you have access. Most applications that write to file will prohibit other applications from concurrently writing to that file, so the 'UserWrite' attribute should be a good indicator for checking whether or not the external application has completed writing to the file.

Please refer to the documentation link below for more information on 'fileattrib' function:

http://www.mathworks.com/help/matlab/ref/fileattrib.html

For example:

>>[stat,struc] = fileattrib('D:\work\results\mydatafile')
stat =
     1
struc = 
            Name: 'D:\work\results\mydatafile'
         archive: 0
          system: 0
          hidden: 0
       directory: 1
        UserRead: 1
       UserWrite: 1
     UserExecute: 1
       GroupRead: NaN
      GroupWrite: NaN
    GroupExecute: NaN
       OtherRead: NaN
      OtherWrite: NaN
    OtherExecute: NaN

The operation is successful as indicated by the status, stat, value of 1. The structure, struc, contains the file attributes.

Related Solutions

MATLAB: How to check if I have read or write access to a directory

The "fileattrib" function is written as a wrapper for the DOS "attrib" command on Windows. "attrib" cannot do all the operations that you expect and checking read or write access for directories may not return the expected result. Therefore, when you do "fileattrib" on a directory, "UserRead" and "UserWrite" does not reliably report the read and write access to the directory in question.

One workaround to check read access to a folder is:

exist( myfolder, 'dir' ) && ~isempty( dir( myfolder ) )

To check if the user has write permission:

fileName = '\\path\to\my\folder\tmpFile.txt';
[fid,errmsg] = fopen(fileName, 'w');
if ~isempty(errmsg)&&strcmp(errmsg,'Permission denied') 
    fprintf('\nError: You do not have write permission to the folder (%s).\n',fileName);
else
    fclose(fid);
    delete(fileName);
end

Disclaimer : The above script deletes the file. Please take a backup of the file before running the script

MATLAB: Renaming files using MATLAB

From MATLAB, you can use the "movefile" function to rename files on your machine:

https://www.mathworks.com/help/releases/R2020a/matlab/ref/movefile.html

For more information on managing files and folders in MATLAB see this documentation:

https://www.mathworks.com/help/releases/R2020a/matlab/matlab_env/manage-files-and-folders.html

Alternatively, you can use the "system" command which executes on the local operating system.

On Windows using CMD, the "rename" command works like this:

C:> rename  file_path  new_name
C:> rename  C:\Temp\file1.txt file2.txt

So in MATLAB, from the directory with the file you could execute:

>> system("rename " + "old_name.txt" + " " + "new_name.txt")

If the file names contain spaces, this can confuse the operating system, so a more robust approach is to wrap each file name in double quotes like this:

>> system("rename " + '"' + "old name.txt" + '" "' + "new name.txt" + '"')

This produces a system command like this:

C:> rename "old name.txt" "new name.txt"

To use MATLAB variables for the old and new file names you can use these MATLAB commands:

>> old_path_to_file = "C:\Temp\test a.txt";

>> new_filename = "test b.txt";

>> cmd = "rename " + '"' + old_path_to_file + '" "' + new_filename + '"';

>> system(cmd);

On a Linux or macOS (Unix) system, this would be:

>> old_path_to_file = "/tmp/test a.txt";
>> new_filename = "test b.txt";
>> cmd = "mv " + '"' + old_path_to_file + '" "' + new_filename + '"';
>> system(cmd);

Best Answer

Related Solutions

MATLAB: How to check if I have read or write access to a directory

MATLAB: Renaming files using MATLAB

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