how edit and write into particular line consisting of letters and numbers text file using matlab?

** BOUNDARY CONDITIONS
** 
** Name: Surf_temp1 Type: Temperature
*Boundary
Surf_temp_Set-1, 11, 11, 100.
** Name: Surf_temp2 Type: Temperature
*Boundary
Surf_temp_Set-2, 11, 11, 100.
** Name: Surf_temp3 Type: Temperature
*Boundary
Surf_temp_Set-3, 11, 11, 100.
** Name: Surf_temp4 Type: Temperature
*Boundary
Surf_temp_Set-4, 11, 11, 500.
This is text file to be edited. How to search particular boundary condition and edit and write to new text file?..Suppose I want to change 
*Boundary
Surf_temp_Set-4, 11, 11, 500.
as
*Boundary
Surf_temp_Set-4, 11, 11, 350.

Answer 1

[KSSV]

f= fopen('your data in text file'); 
c = textscan(f,'%s','delimiter','\n'); 
fclose(f) ;
S = c{1} ;
%
str = {'Surf_temp_Set-4, 11, 11, 350.'} ; % to be replaced 
str1 = strsplit(str{1}) ;
% get the index which is to be repalced 
idx1 = find(not(cellfun('isempty',strfind(S, str1{1}))));  
%  Repalce
S(idx1) = str ;
% write to a rext file
fid = fopen('file.txt','w') ;
fprintf(fid,'%s\n',S{:});
fclose(fid) ;

[raghavendra g g]

Thank you KSSV. In this line Surf_Set_4, 11, 11, 350.... the last number 350 need to be updated for every iterations like it changes to 400,500,600,700. how to do this?

Answer 2

[Walter Roberson]

Unfortunately, the only way to update a text file in MATLAB is to read in the old file, make whatever changes you need, and write out a new file containing the new content.

It is safer to always write to a different file, not the input file, in case something goes wrong during the writing (bug, system fails, disk fills up.)

This inability to effectively update a text file in place is due to the way that text files have been represented in nearly all systems since about the time that room-sized computers started being replaced by smaller computers.