Next Available Filename

Return the next unused filename, incrementing an integer as required.

NEXTNAME returns a filename, incrementing a numbered suffix such that the returned name is not currently used by any file or folder.

On occasion it may be required to save files without knowing or requiring a particular number sequence, for example when saving interim results or backups during large calculations. Using an internal counter is one option, but this does not work when there are already existing files with the same names, or when the code is stopped-and-started unpredictably (e.g throws errors while calculating and is restarted). This function offers one simple solution: NEXTNAME will search for existing files/folders that match the provided inputs, increment an integer until the value is unused by any current filename, and then return the next unused filename.

Note that unlike some other submissions on FEX, this function compares the number values, not the literal filenames! This means you will not get "x001" if e.g. "x1" or "x01" or "x00000001" already exist in the specified location.

Syntax 1

One text input is required: the folder/filename (including file extension, if required). The folder/filename must include one integer within angle brackets (aka less/greater than characters), e.g.: 'test<01>.txt'. The integer will be incremented as required to define an unused filename. The angle brackets are not returned in the output.

Syntax 2

Three text inputs are required:

1. The basic folder/filename, without any file extension.
2. The suffix, which must contain one integer. Some examples of suffixes are: '0', '_1', '(5)', '-0001-backup', '_temp1', etc. This suffix will be appended to the folder/filename, before the file extension, after incrementing the integer as required to define an unused filename.
3. The file extension, if required. For folders (or files without extensions) use '' or "".

Note the path, name, and extension inputs can generally be obtained from a filename using FILEPARTS.

Integer

The integer specifies:

* the value to start incrementing from (this can be zero or any positive integer, i.e. 0, 1, 2, 3, etc.),

* the minimum width of the output number by using leading zeros as required. For example, "001" specifies the integer in the output has (minimum) width of three characters. The output integer will be automatically zero padded (if required) to this length.

Examples

% Current directory contains files 'A1.txt', 'A2.txt', and 'A4.txt':

>> nextname("A<1>.txt")                 % syntax 1
ans = "A3.txt"
>> nextname("A","1",".txt")             % syntax 2
ans = "A3.txt"

>> nextname("A<001>.txt")               % syntax 1
ans = "A003.txt"
>> nextname("A","001",".txt")           % syntax 2
ans = "A003.txt"

% Directory 'test' contains subdirectories 'B(1)', 'B(2)', and 'B(4)':

>> nextname('test/B(<1>)')              % syntax 1
ans = 'B(3)'
>> nextname('test/B','(1)','')          % syntax 2
ans = 'B(3)'
>> nextname('test','B(<1>)')            % syntax 1
ans = 'B(3)'
>> nextname('test','B','(1)','')        % syntax 2
ans = 'B(3)'

>> nextname('test','B(<1>)',true)       % syntax 1
ans = 'test/B(3)'
>> nextname('test','B','(1)','',true)   % syntax 2
ans = 'test/B(3)'