How to determine the line-number in a file that contains specific statements

Question

Homayoon 2016-3-24

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https://ww2.mathworks.cn/matlabcentral/answers/275222-how-to-determine-the-line-number-in-a-file-that-contains-specific-statements

编辑： KSSV 2016-3-24

采纳的回答： KSSV

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Dear All,

I do have a file that has a line starting with the following statement:

I Need This Line

What I need is to locate the line number of this line and fgetl of the file from beginning to this line(including this line). What should I do? Basically the problem here is the location of the wanted line varies from one file to another so that it makes way too difficult for me to obtain the information I want. Please be advised that I used fopen command to open my input file. Thank you so much

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Homayoon 2016-3-24

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no in fact I got what you suggested but does not work

I used this code

for c=1:19
      line=fgets(fid) 
      if (strcmp(line,'I Need This Line')==1)
       %take this c
      end
    end

But it reads the content of all of my lines as -1 which I do not know why

KSSV 2016-3-24

You are not opening the file properly....what is fid value? It shall be +ve. Cross check the value of line with your file.

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Answer 1

KSSV 2016-3-24

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编辑：KSSV 2016-3-24

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Junk.txt

Homayoon you may try the following code with the attached txt file.

file = 'Junk.txt' ;
fid = fopen(file,'r') ;
str = 'I Need This Line' ;
for c=1:13
    line=strtrim(fgets(fid)) ;
    if strcmp(line,str)
        iwant = c ;
    end
end
fclose(fid) ;
iwant is the line number you wanted.

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Answer 2

Orion 2016-3-24

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Hi,

I guess you need something like that.

Assuming you have a .txt file : MyTextFiles.txt, that contains :

ruiez
gjrigj
rjigjri
I Need This Line and the rest of it ?
gjijri
pzepaz

you need a code like that :

% Open and read the content
Myfile = 'MyTextFiles.txt';
fid = fopen(Myfile);
Text = textscan(fid,'%s','delimiter','\n');
Text = Text{1};
fclose(fid);
% pattern to find at the beginning of a line
pattern = 'I Need This Line';
% analyze
found = 0;
for i = 1:length(Text)
   if strncmp(Text{i},pattern,length(pattern))
       found = i;
       break;
   end
end
% result
if found
    fprintf('pattern at line %d\n',found)
else
    fprintf('pattern not found')
end