file parsing identifier need to choose the correct identifier

i have this file

04_T_A_tx01_3009.txt

and my current code selects it base on identifier = 'tx'; for parsing

the correct selection would be tx01 but its selectiong both tx01 and txt

what can i do to just select tx#, theres more than just 01 and it changes

where i am using the identifier

parsed_location = strfind(parsed_data,channel_identifier);

number_location = find(~cellfun(@isempty,parsed_location)); at this point i am getting two finds i want just to find the first tx#

channel_digits = regexp(parsed_data{channel_location} , '\d', 'match');

Answer 1

[millercommamatt]

st = '04_T_A_tx01_3009.txt';
id_cell = regexp(st,'tx\d+','match');
id_char = id_cell{1};