Regexp to filter file names

Question

maxroucool 2017-10-19

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https://ww2.mathworks.cn/matlabcentral/answers/362214-regexp-to-filter-file-names

评论： maxroucool 2017-10-20

Hello,

I would like to use a regexp to filter file names contained in a folder. I almost got it, but I have trouble handling cell that output the dir() function...

Let's imagine I have these files in the data folder :

DY463269-F 01-01-2017.xlsx
DY463269-F 01-01-2017.xlsx
DY463271-8 01-01-2017.xlsx
DY466290-M 01-01-2017.xlsx

My code is :

filesList = dir('data/');
serialList = regexpi({filesList.name}, '[a-z]{2}[0-9]{6}[a-z\-]{0,2}', 'match')
dateList = regexpi({filesList.name}, '[0-9]{2}-[0-9]{2}-[0-9]{2}', 'match')
data = cell2struct([serialList; dateList],{'Name','Date'},1)
data(3).Name

First, I guess we can do only one regexpi to get both information... But mostly, data(3).Name return me a cell and I would like it to simply be a string.

Any idea to fix this?

Thanks,

Max

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Answer 1

Walter Roberson 2017-10-19

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filenames = {'DY463269-F 01-01-2017.xlsx'
         'DY463269-F 01-01-2017.xlsx'
         'DY463271-8 01-01-2017.xlsx'
         'DY466290-M 01-01-2017.xlsx'};
fileinfo_cell = regexpi( filenames, '^(?<serial>[a-z]{2}\d{6}[a-z\-]{0,2})\s+(?<date>\d\d-\d\d-\d\d)', 'names','lineanchors');
fileinfo = vertcat(fileinfo_cell{:});

fileinfo will then be a struct array with fields "serial" and "date".

With that particular set of data, the struct will have 3 elements, because DY463271-8 01-01-2017.xlsx does not match the pattern (the serial ends in -8 but the pattern does not permit numbers at that point.)

A generalization of the pattern would be

fileinfo = regexpi( filenames, '^(?<serial>\w\w\d{6}[\w-]{0,2})\s+(?<date>\d\d-\d\d-\d\d)', 'names','lineanchors')

Each \w corresponds to [a-z0-9_] -- the "word-building" characters. What you have now is more focused and you might need that focus, but sometimes it is useful to be more lenient.

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maxroucool 2017-10-20

Perfect thank you Walter!

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Answer 2

Guillaume 2017-10-19

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https://ww2.mathworks.cn/matlabcentral/answers/362214-regexp-to-filter-file-names#answer_286705

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Note that the reason you get cell arrays in your structure is because as you've used it regexpi returns a cell array of cell arrays of char arrays as there can be more than one match per filename. Adding the 'once' option to these regexpi calls would tell them that there can only ever be more than one match and as a result you'd get a cell array of char arrays, which would give you the structure you expect.

serialList = regexpi({filesList.name}, '[a-z]{2}[0-9]{6}[a-z\-]{0,2}', 'match', 'once');
dateList = regexpi({filesList.name}, '[0-9]{2}-[0-9]{2}-[0-9]{2}', 'match', 'once');