How to sort property -value pair in alphabetical order with Matlab

Question

I want to add a property-value pair to existing file. In the mean time all the properties should be ordered in alphabetical order. For example :

[Info] % proper         


        

Answer 1

How about read the file into a struct?

function fileData = readFileIntoStruct( fileName )
%
% read [property] value pairs file into struct
% 
fh = fopen( fileName, 'r' ); % read handle
line = fgetl( fh );
while ischar( line )
    % property
    tkn = regexp( line, '\[([^\]+)]\]', 'once', 'tokens' );
    % read next line for value
    val = fgetl( fh );
    fileDate.(tkn{1}) = val;
    line = fgetl( fh ); % keep reading
end
fclose( fh ); % don't forget to close the file at the end.

Now you have all the data as a struct with properties as fieldnames and values as the field value.

Now you can update a property simply by:

function fileData = updateProperty( fileData, propName, newVal )
if isfield( fileData, propName )
    fileData.(propName) = newVal;
else
    warning( 'property %s does not exist - please add it first', propName );
end

You can add a property:

function fileData = addProperty( fileData, propName, newVal )
if ~isfield( fileData, propName )
    fileData.(propName) = newVal;
else
    warning ( 'property %s already exists, use update to change its value', propName );
end

You can sort the properties alphabetically using orderfields:

fileData = orderfields( fileData );

You can write the struct back to file simply using:

function writeDataToFile( newFileName, fileData )
fopen( newFileName , 'w' ); %write handle
propNames = fieldnames( fileData );
for ii = 1:numel( propNames )
    fprintf( fh, '[%s]\r\n%s\r\n', propNames{ii}, fileData.(propNames{ii}) );
end
fclose( fh ); 

Assumptions:

1. The properties' names are legitimate Matlab field names (see variable naming for details).

2. The value of each property is always a string.

3. I did not include any error-checking code in these examples (files not found, wrongly formatted strings, etc.)

4. I assume the input file is strictly "[prop] val" pairs without any additional comments etc.