MATLAB: How load a list of filenames from .txt file - string

Question

filelist.txt contains a list of files:
/path/file1.json
/path/file2.json
/path/fileN.json
Is there a (simple) MATLAB command that will accept filelist.txt and read each file as a string and store each string into a cell array?

Answer 1

Just use readtable, asking it to read each line in full.
>> tbl = readtable('filelist.txt','ReadVariableNames',false,'Delimiter','\n');
>> tbl.Properties.VariableNames = {'filenames'}
tbl =
3×1 table
filenames
__________________
'/path/file1.json'
'/path/file2.json'
'/path/fileN.json'
Then access the elements in a loop
for idx = 1:height(tbl)
this_filename = tbl.filenames{idx};
end

Answer 2

This problem is a bit to specific for a standard function. However, it is easily doable with the combination of two functions:
First, you have to open the file:
fid = fopen('filelist.txt');
Next you can read line by line with:
line_ex = fgetl(fid)
This function includes a counter. If you call the function the next time, it will read the second line and so on. You find more information here.
The whole code might look like this:
% Open file
fid = fopen('testabc');
numberOfLines = 3;
% Preallocate cell array
line = cell(numberOfLines, 1);
% Read one line after the other and save it in a cell array
for i = 1:numberOfLines
line{i} = fgetl(fid);
end
% Close file
fclose(fid);

Answer 3

For this replace the for loop with a while loop:
i=0;
while ~feof(fid)
i=i+1
line{1} = fgetl(fid)
end

Answer 4

Alternative to while loop: Retrieve the number of lines and use in Caduceus' for-loop:
% Open file
fid = fopen('testabc');
numberOfLines = numlinestextfile('testable'); % function defined below
% Preallocate cell array
line = cell(numberOfLines, 1);
% Read one line after the other and save it in a cell array
for i = 1:numberOfLines
line{i} = fgetl(fid);
end
% Close file
fclose(fid);
Custom function:
function [lineCount] = numlinestextfile(filename)
%numlinestextfile: returns line-count of filename
% Detailed explanation goes here
if (~ispc) % Tested on OSX
evalstring = ['wc -l ', filename];
% [status, cmdout]= system('wc -l filenameOfInterest.txt');
[status, cmdout]= system(evalstring);
if(status~=1)
scanCell = textscan(cmdout,'%u %s');
lineCount = scanCell{1};
else
fprintf(1,'Failed to find line count of %s\n',filenameOfInterest.txt);
lineCount = -1;
end
else
if (~ispc) % For Windows-based systems
[status, cmdout] = system(['find /c /v "" ', filename]);
if(status~=1)
scanCell = textscan(cmdout,'%s %s %u');
lineCount = scanCell{3};
disp(['Found ', num2str(lineCount), ' lines in the file']);
else
disp('Unable to determine number of lines in the file');
end
end
end