downloading files from a website with conditions on names of files

5 views (last 30 days)
Question: I work on a website https://www.somecompany.com/xml/.
This directory has files whose filename starts with a letter "A" and "B".
The filenames in the directory are like:
A_20080403.xml
A_20080403_1.xml
A_20080403_2.xml
A_20080404_1.xml
B_20080403_1.xml
That is
  • Filenames are of the form "Capital letters"+"_"+"date"+"_"+"numbers".xml or "Capital letters"+"_"+"date".xml
  • There are dates that do not have corresponding files
I would like to download all the files whose filenames start with a letter "A".
What has been tried:
(a) I was able to save a single file using "websave" command.
for k = 20080401:20100101
filename = sprintf('A%d.xml', k);
url = ['https://www.somecompany.com/xml/' filename];
outfilename = websave(filename,url);
end
Problems with the above code: The above code does not work because
  • This code assumes the filename of the form "Capital letters"+"date".xml and not the filenames that explained above
  • This code returns the error for a date when there are no corresponding files and stops then
How shall one improve the above code?

Answers (1)

Walter Roberson
Walter Roberson on 9 Feb 2022
It would be more robust / faster if the site provided a way to list the available files, instead of having to do trial and error.
baseurl = "https://www.somecompany.com/xml/";
datelimits = datetime({'20080401', '20100101'}, 'InputFormat', 'yyyyMMdd');
subfile_limit = 5; %no more than _5 -- adjust as appropriate
subfile_modifier = ["", "_" + (1:subfile_limit)] + ".xml";
for Day = datelimits(1):datelimits(2)
daystr = string(Day);
for Sub = subfile_modifier
filename = "A_" + daystr + Sub;
url = baseurl + filename;
try
outfilename = websave(filename,url);
fprintf('fetched %s\n', filename);
catch
break; %skip remaining subfiles for this date upon first failure
end
end
end
  2 Comments
alpedhuez
alpedhuez on 12 Mar 2022
When I ran the code above, I got the value of
daystr "01-Jan-2010"
filename "A_01-Jan-2010.xml"
But the filename is, as noted above, of the format of
A_20100101.xml
Thus one needs to modify the process of assigning the variable daystr.
Walter Roberson
Walter Roberson on 12 Mar 2022
datelimits = datetime({'20080401', '20100101'}, 'InputFormat', 'yyyyMMdd', 'Format', 'yyyyMMdd');

Sign in to comment.

Categories

Find more on Downloads in Help Center and File Exchange

Tags

Products


Release

R2021b

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!