Extraction of portion of textfile

I have text string stored in a variable. The text file is just an example but, the .txt(s) I will work on may not always start with the same string code. I want to delete all the strings above the first $GPGLL, if this is not the first, and I want to delete all the strings below the last $SDDBT string and store in a new variable, below is my original variable, the number of strings is not always the same. Thumbs up for the good samaritan that will help me in this task.

new_variable= $GPHDT,9.420,T*3A $GPGLL,5340.91664087,N,00713.79587546,E,073418.00,A,D*62 $GPVTG,193.15,T,,M,5.72,N,10.59,K,D*0A $GPHDT,9.420,T*3A $SDDPT,0001.5,000.0*63 $SDDBT,00004.9,f,0001.5,M,0000.8,F*07 $SDDBS,00004.9,f,0001.5,M,0000.8,F*00 $VWVHW,,T,,M,00.0,N,,K*4A $SDRMB,A,13.74,L,00,TEST1,5330.546,N,00807.276,E,033.4,108,,*45 $GPGLL,5340.91664087,N,00713.79587546,E,073418.00,A,D*62 $GPHDT,9.421,T*3B $GPVTG,193.65,T,,M,5.82,N,10.77,K,D*0E $GPVTG,192.06,T,,M,5.54,N,10.26,K,D*05 $GPHDT,9.428,T*32 $GPGLL,5340.91360433,N,00713.79468132,E,073420.00,A,D*64 $GPHDT,9.430,T*3B .35,K,D*0F $GPHDT,9.431,T*3A $SDDPT,0001.4,000.0*62 $SDDBT,00004.5,f,0001.4,M,0000.7,F*05004.5,f,0001.4,M,0000.7,F*02 $VWVHW,,T,,M,00.0,N,,K*4A $SDRMB,A,13.74,L,00,TEST1,5330.546,N,00807.276,E,033.4,108,,*45 $GPGLL,5340.91207731,N,00713.79413391,E,073421.00,A,D*63 $GPHDT,9.433,T*38 $GPVTG,193.32,T,,M,5.69,N,10.54,K,D*08 $GPHDT,9.435,T*3E $GPGLL,5340.91056222,N,00713.79354123,E,073422.00,A,D*6E $SDDPT,0002.0,000.0*65 $SDDBT,00006.5,f,0002.0,M,0001.0,F*06 $SDDBS,00006.5,f,0002.0,M,0001.0,F*01 $VWVHW,,T,,M,00.0,N,,K*4A $SDRMB,A,13.75,L,00,TEST1,5330.546,N,00807.276,E,033.4,108,,*44 $GPHDT,9.437,T*3C $GPVTG,191.91,T,,M,5.51,N,10.20,K,D*0B $GPHDT,9.439,T*32 *3D $GPVTG,194.87,T,,M,5.32,N,9.86,K,D*38 $GPHDT,9.443,T*3F $GPGLL,5340.90756479,N,00713.79236750,E,073424.00,A,D*61 $GPHDT,9.446,T*3A $SDDPT,0002.1,000.0*64 $SDDBT,00006.8,f,0002.1,M,0001.1,F*0B $SDDBS,00006.8,f,0002.1,M,0001.1,F*0C $VWVHW,,T,,M,00.0,N,,K*4A $SDRMB,A,13.75,L,00,TEST1,5330..4,108,,*44 $GPVTG,194.65,T,,M,5.49,N,10.17,K,D*08 $GPHDT,9.449,T*35 $GPGLL,5340.90609055,N,00713.79168827,E,073425.00,A,D*66 $GPHDT,9.452,T*3F $GPVTG,193.15,T,,M,5.52,N,10.22,K,D*04 $GPHDT,9.454,T*39 $SDDPT,0002.4,000.0*61 $SDDBT,00007.8,f,0002.4,M,0001.3,F*0D $SDDBS,00007.8,f,0002.4,M,0001.3,F*0A $VWVHW,,T,,M,00.0,N,,K*4A $SDRMB,A,13.75,L,00,TEST1,5330.546,N,00807.276,E,033.4,108,,*44 $GPGLL,5340.90462662,N,00713.79106230,E,073426.00,A,D*6C

Answer 1

[Andrei Bobrov]

f = fopen('nameYourTextFile.txt');
c = textscan(f,'%s','delimiter','\n');
fclose(f);

out = c{:}(find(strncmp(c{:},'$GPGLL',6),1,'first')...
                                     :find(strncmp(c{:},'$SDDBT',6),1,'last'));

ADD

new_variable= '$GPHDT,9.420,T*3A $GPGLL,5340.91664087,N,00713.79587546,E,073418.00,A,D*62 $GPVTG,193.15,T,,M,5.72,N,10.59,K,D*0A $GPHDT,9.420,T*3A $SDDPT,0001.5,000.0*63 $SDDBT,00004.9,f,0001.5,M,0000.8,F*07 $SDDBS,00004.9,f,0001.5,M,0000.8,F*00 $VWVHW,,T,,M,00.0,N,,K*4A $SDRMB,A,13.74,L,00,TEST1,5330.546,N,00807.276,E,033.4,108,,*45 $GPGLL,5340.91664087,N,00713.79587546,E,073418.00,A,D*62 $GPHDT,9.421,T*3B $GPVTG,193.65,T,,M,5.82,N,10.77,K,D*0E $GPVTG,192.06,T,,M,5.54,N,10.26,K,D*05 $GPHDT,9.428,T*32 $GPGLL,5340.91360433,N,00713.79468132,E,073420.00,A,D*64 $GPHDT,9.430,T*3B .35,K,D*0F $GPHDT,9.431,T*3A $SDDPT,0001.4,000.0*62 $SDDBT,00004.5,f,0001.4,M,0000.7,F*05004.5,f,0001.4,M,0000.7,F*02 $VWVHW,,T,,M,00.0,N,,K*4A $SDRMB,A,13.74,L,00,TEST1,5330.546,N,00807.276,E,033.4,108,,*45 $GPGLL,5340.91207731,N,00713.79413391,E,073421.00,A,D*63 $GPHDT,9.433,T*38 $GPVTG,193.32,T,,M,5.69,N,10.54,K,D*08 $GPHDT,9.435,T*3E $GPGLL,5340.91056222,N,00713.79354123,E,073422.00,A,D*6E $SDDPT,0002.0,000.0*65 $SDDBT,00006.5,f,0002.0,M,0001.0,F*06 $SDDBS,00006.5,f,0002.0,M,0001.0,F*01 $VWVHW,,T,,M,00.0,N,,K*4A $SDRMB,A,13.75,L,00,TEST1,5330.546,N,00807.276,E,033.4,108,,*44 $GPHDT,9.437,T*3C $GPVTG,191.91,T,,M,5.51,N,10.20,K,D*0B $GPHDT,9.439,T*32 *3D $GPVTG,194.87,T,,M,5.32,N,9.86,K,D*38 $GPHDT,9.443,T*3F $GPGLL,5340.90756479,N,00713.79236750,E,073424.00,A,D*61 $GPHDT,9.446,T*3A $SDDPT,0002.1,000.0*64 $SDDBT,00006.8,f,0002.1,M,0001.1,F*0B $SDDBS,00006.8,f,0002.1,M,0001.1,F*0C $VWVHW,,T,,M,00.0,N,,K*4A $SDRMB,A,13.75,L,00,TEST1,5330..4,108,,*44 $GPVTG,194.65,T,,M,5.49,N,10.17,K,D*08 $GPHDT,9.449,T*35 $GPGLL,5340.90609055,N,00713.79168827,E,073425.00,A,D*66 $GPHDT,9.452,T*3F $GPVTG,193.15,T,,M,5.52,N,10.22,K,D*04 $GPHDT,9.454,T*39 $SDDPT,0002.4,000.0*61 $SDDBT,00007.8,f,0002.4,M,0001.3,F*0D $SDDBS,00007.8,f,0002.4,M,0001.3,F*0A $VWVHW,,T,,M,00.0,N,,K*4A $SDRMB,A,13.75,L,00,TEST1,5330.546,N,00807.276,E,033.4,108,,*44 $GPGLL,5340.90462662,N,00713.79106230,E,073426.00,A,D*6C';

ccc = mat2cell(new_variable,1,diff([regexp(new_variable,'\$'),...
                                            numel(new_variable)+1]))';
out = ccc(find(strncmp(ccc,'$GPGLL',6),1,'first'):...
                              find(strncmp(ccc,'$SDDBT',6),1,'last'));

[mb1400]

??? Error using ==> strncmp Too many input arguments.

that's what it returns

[Andrei Bobrov]

Please, see ADD part in my answer.