How to have a variable format spec print length when using fprintf?

I am trying to print column header information to a .txt file using fprintf. I am importing the column header information from another file. The problem is that the imported column header information can be any character length, as defined by the user (e.g. could be 1 character long, could be 20). I would like to use the maximum header length to define how much space will be needed when printing the column headers/labels. The code in question is summarized below:

for i = 1:length(headerinformation)
    fprintf(fid,'%10s',headerinformation{i})
end

The default amount of space I am using is 10 (i.e. %10s), but this doesn't work well when the headers are > 10. At first i tried using the maximum header lenth variable to define the maximum header length, but this didn't work properly when using the fprintf format spec. I tried something similar to the following:

MaxHeaderLength = max(cell2mat(columnheaderlength));
for i = 1:length(headerinformation)
    fprintf(fid,'%(%i)s',headerinformation{i}, MaxHeaderLength) %parenthesis around %i added for explanation only, i know this wouldn't actually work
end

Any guidance would be appreciated.

Answer 1

[Jess Lovering]

Would this work for what you need?

MaxHeaderLength = max(cell2mat(columnheaderlength));

max_fmt_spec = ['%' num2str(MaxHeaderLength) 's'];

for i = 1:length(headerinformation)

fprintf(fid,max_fmt_spec,MaxHeaderLength)

end