Find files of a certain extension and populate a structure field with those file names.

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Allen Hammack
Allen Hammack on 18 Mar 2022
Commented: Voss on 18 Mar 2022
I have a directory with multiple .txt files. I want find all those .txt files and create a structure field with the names of those files. I've tried the following:
>> dir(strcat(pwd,'\','*.txt'))
Test_1.txt Test_2.txt Test_3.txt
>> struct1.file_names = dir(strcat(pwd,'\','*.txt'))
struct1 =
struct with fields:
file_names: [3×1 struct]
>> struct1.file_names
ans =
3×1 struct array with fields:
name
folder
date
bytes
isdir
datenum
I don't understand why these three commands:
dir(strcat(pwd,'\','*.txt'))
struct1.file_names = dir(strcat(pwd,'\','*.txt'))
struct1.file_names
produce different outputs. I also don't know how to populate struct1.file_names with the names of my .txt files. Can someone please help?

Accepted Answer

Scott MacKenzie
Scott MacKenzie on 18 Mar 2022
Edited: Scott MacKenzie on 18 Mar 2022
Your second command is wrong. The dir command returns a structure. You don't need to append ".file_names". The filenames are part of the structure returned by dir. Try this:
struct1 = dir(strcat(pwd,'\','*.txt')) % show the structure returned by dir
struct1.name % show the filenames within the structure returned by dir

More Answers (1)

Voss
Voss on 18 Mar 2022
dir() with no output argument (i.e., not assigning the result to any variable) displays the result to the command line.
S = dir() with an output argument (i.e., assigning to the variable S in this case) gives you an array of structs, each element of which corresponds to one item (that is, one file or folder) and contains the file (or folder) name as well as other information.
Assigning the output of your dir() call (rewritten here to use fullfile()) to a variable seems like it will give you the information you want
struct1 = dir(fullfile(pwd(),'*.txt'))
struct1 = 0×1 empty struct array with fields: name folder date bytes isdir datenum
names = {struct1.name}
names = 0×0 empty cell array
struct1 = dir() % get everything, not just .txt files
struct1 = 2×1 struct array with fields:
name folder date bytes isdir datenum
names = {struct1.name}
names = 1×2 cell array
{'.'} {'..'}

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