How to delete lines before a particular character from .txt files?

I have 100 files. I want to delete the lines before the word 'pressure' from all the files. The number of lines before the word 'pressure' is different in different files. A sample file if attached. Thanks in advance.

Answer 1

[Stephen23]

A straight-forward line-by-line method:

[fii,msg] = fopen('tdump18020910.txt','rt');
assert(fii>=3,msg)
[fio,msg] = fopen('tdump_new.txt','wt');
assert(fio>=3,msg)
boo = false;
while ~feof(fii)
    str = fgetl(fii);
    boo = boo || ~isempty(strfind(str,'PRESSURE'));
    if boo
        fprintf(fio,'%s\n',str);
    end
end
fclose(fii);
fclose(fio);

The input and output files are attached. Too loop over multiple files simply use one of the two methods given in the MATLAB documentation:

https://www.mathworks.com/help/matlab/import_export/process-a-sequence-of-files.html

For example, using dir:

S = dir('*.mat);
for k = 1:numel
    F = S(k).name;
    ... remove lines
end

[Debayan Mandal]

Thank you for your response. I want this change in the input file(s). Is it possible to do so?

[Stephen23]

"I want this change in the input file(s). Is it possible to do so?"

It is not very clear what you are asking, but I suspect that you want to apply this code to multiple files automatically, in which case the answer is: read the last part of my answer and the link that I gave. you to read

Answer 2

[Jan]

File  = 'tdump18020910.txt';
Str   = fileread(File);
CStr  = splitstr(Str, '\n');
match = find(contains(CStr, 'PRESSURE', 'IgnoreCase', true), 1);
[fid, msg] = fopen(File, 'w');
if fid < 0, error('%s', msg); end
fprintf('%s\n', CStr{match:numel(CStr)});
fclose(fid);