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identifying positions of a string within a text file

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I would like to take a text file, which has been saved with various special characters ('e.g. $$') and identify the positions that these characters occupy. Then, I would insert values into those positions. So the file may look like: line $$ 1 $$ line 2
So I would need some way to identify positions 6 and 11, then insert text at those locations.
I've tried various things such as reading the file in a string and converting to a char array while using strfind, but in each case, there is an issue. What would be the best way to overwrite the $$'s with values?

Accepted Answer

Walter Roberson
Walter Roberson on 1 Mar 2011
Probably something like this:
fid = fopen(FileName,'rt');
filetext = fread(fid,'*char');
newtext = regexprep(filetext, '\$\$', 'Hello', 'once');
newtext = regexprep(newtext, '\$\$', 'World', 'once');
fid = fopen(NewFilename, 'wt');
fwrite(fid, newtext, '*char');

More Answers (2)

Brett Shoelson
Brett Shoelson on 1 Mar 2011
Lots of ways. This one uses regular expressions:
mystr = 'line $$ 1 $$ line 2'
newstr = regexprep(mystr,'\$\$','New_String')

Brent on 1 Mar 2011
Thank you both for the quick reply. This is exactly what I needed.


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