How can I prepend text to a file using MATLAB?

I would like to insert new text at the beginning of a file using MATLAB. Is there a function that will do this for me?

Answer 1

[MathWorks Support Team]

While we do not have any built-in routines in our products to do specifically what you want, you may be able to write a MATLAB function that does this.

You will need to do something along the lines of the following:

1. Open a temporary file (see "doc tempname")

2. Write your data there that you wish to prepend

3. Open your original file for reading

4. Read from your original and write to the temporary file

5. Close both files

6. Copy the temporary over the original (see "doc copyfile")

An example is shown below.

function prepend2file( string, filename, newline )

% newline:  is an optional boolean, that if true will append a \n to the end 

% of the string that is sent in such that the original text starts on the 

% next line rather than the end of the line that the string is on 

% string:  a single line string 

% filename:  the file you want to prepend to 

      tempFile = tempname

      fw = fopen( tempFile, 'wt' );

      if nargin < 3

          newline = false;

      end

      if newline

          fwrite( fw, sprintf('%s\n', string ) );

      else

          fwrite( fw, string );

      end

      fclose( fw );

      appendFiles( filename, tempFile );

      copyfile( tempFile, filename );

      delete(tempFile);

% append readFile to writtenFile

function status = appendFiles( readFile, writtenFile )

      fr = fopen( readFile, 'rt' );

      fw = fopen( writtenFile, 'at' );

      while feof( fr ) == 0

          tline = fgetl( fr );

          fwrite( fw, sprintf('%s\n',tline ) );

      end

      fclose(fr);

      fclose(fw);