identifying positions of a string within a text file

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?

Thanks

Answer 1

[Walter Roberson]

Probably something like this:

fid = fopen(FileName,'rt');
filetext = fread(fid,'*char');
fclose(fid);

newtext = regexprep(filetext, '\$\$', 'Hello', 'once');
newtext = regexprep(newtext, '\$\$', 'World', 'once');

fid = fopen(NewFilename, 'wt');
fwrite(fid, newtext, '*char');
fclose(fid);

Answer 2

[Brett Shoelson]

Lots of ways. This one uses regular expressions:

mystr = 'line $$ 1 $$ line 2'
newstr = regexprep(mystr,'\$\$','New_String')

Cheers,

Brett

Answer 3

[Brent]

Thank you both for the quick reply. This is exactly what I needed.