MATLAB: Replace only the first match

replace

I have a txt with 2000 lines. i want to open the txt,scan,find EE1 and replace it(only the first EE1,not the second) then create a new txt and close…
this is something a found but it replace all the EE1 it found.I want to replace only the first match..
 close all;  clear;  clc
 % Set user specific paths and values
% ======================================================================

HFSS_EXE_PATH='C:\Program Files (x86)\Ansoft\HFSS12';
SCRIPT_PATH='c:\HFSS\scriptttt.vbs';
NEW_VBS_FILE='c:\HFSS\scrip.vbs';
% ======================================================================
 cc=0;
 for wg_y=6:1:8
   cc=cc+1;
   % Replace first occurrence of waveguide Y dimension
   %vbs_str=file2str(SCRIPT_PATH);
  fid1=fopen(SCRIPT_PATH,'r+');
 vbs_str=fscanf(fid1,'%c');
 old_str=('Array("NAME:XSize", "Value:=", "EE1"');
new_str=sprintf('Array("NAME:XSize", "Value:=", "%1.0fmm")',wg_y);
new_vbs_str=strrep(vbs_str,old_str,new_str);
   % Create updated VB script file
  fid=fopen(NEW_VBS_FILE,'w');
    fprintf(fid,'%s',new_vbs_str);                                                                               
  fclose(fid);
 end
Thank you…

Best Answer

index   = strfind(vbs_str, old_str);
first   = index(1);
vbs_str = [vbs_str(1:first - 1), new_str, vbs_str(first + length(old_str):end)];
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