Extract text between single quotes in MATLAB

Question

I have multiple lines in some text files such as

.model sdata1 s tstonefile='../data/s_element/isdimm_rcv_via_2port_via_minstub.s50p' passive=2

I want to extract the text between the single quotes in MATLAB.

Much help would be appreciated.

Answer 1

To get all of the text inside multiple '' blocks, regexp can be used as follows:

regexp(txt,'''(.[^'']*)''','tokens')

This says to get text surrounded by ' characters, which does not include a ' in the captured text. For example, consider this file with two lines (I made up different file name),

txt = ['.model sdata1 s tstonefile=''../data/s_element/isdimm_rcv_via_2port_via_minstub.s50p'' passive=2 ', char(10), ...
'.model sdata1 s tstonefile=''../data/s_element/isdimm_rcv_via_3port_via_minstub.s00p'' passive=2']
>> stringCell = regexp(txt,'''(.[^'']*)''','tokens');
>> stringCell{:}
ans = 
    '../data/s_element/isdimm_rcv_via_2port_via_minstub.s50p'
ans = 
    '../data/s_element/isdimm_rcv_via_3port_via_minstub.s00p'
>> 

Trivia:

• char(10) gives a newline character because 10 is the ASCII code for newline.
• The . character in regexp (regex in the rest of the coding word) pattern usually does not match a newline, which would make this a safer pattern. In MATLAB, a dot in regexp does match a newline, so to disable this, we could add 'dotexceptnewline' as the last input argument to `regexp``. This is convenient to ensure we don't get the text outside of the quotes instead, but not needed since the first match sets precedent.
• Instead of excluding a ' from the match with [^''], the match can be made non-greedy with ? as follows, regexp(txt,'''(.*?)''','tokens').

Answer 2

If you plan to use textscan:

fid = fopen('data.txt','r');
rawdata = textscan(fid,'%s','delimiter','''');
fclose(fid);

output = rawdata{:}(2)

As also used in other answers the single apostrophe 'is represented by a double one: '', e.g. for delimiters.

considering the comment:

fid = fopen('data.txt','r');
rawdata = textscan(fid,'%s','delimiter','\n');
fclose(fid);

lines = rawdata{1,1};
L = size(lines,1);
output = cell(L,1);
for ii=1:L
    temp = textscan(lines{ii},'%s','delimiter','''');
    output{ii,1} = temp{:}(2);
end

Answer 3

One easy way is to split the string with single quote delimiter and take the even-numbered strings in the output:

str = fileread('test.txt');
out = regexp(str, '''', 'split');
out = out(2:2:end);

Answer 4

You can do this using regular expressions. Assuming that there is only one occurrence of text between quotation marks:

% select all chars between single quotation marks.
out = regexp(inputString,'''(.*)''','tokens','once');

Answer 5

After identifing which lines you want to extract info from, you could tokenize it or do something like this if they all have the same form:

test='.model sdata1 s tstonefile=''../data/s_element/isdimm_rcv_via_2port_via_minstub.s50p'' passive=2';
a=strfind(test,'''')
test=test(a(1):a(2))