filename = input('Enter your filename ending in .txt: ', 's');
s1 = '.txt';
s2 == 'filename' % <-- I think you're confused on = versus == here
tf == strcmp(s1,s2) % <-- and here
if tf == 0
filename = input('Enter your filename ending in .txt: ', 's');
end
You can achieve this quite simply with:
filename = input(___);
while ~endsWith(filename,".txt")
filename = input(___);
end
endsWith was introduced in R2016b, and double quotes to create strings in R2017a.
