UNIX for Beginners Questions & Answers

x,999999,429,,,,,,,,,,,,,,,,,,,,9999999,999999,xxxxxxxx,,xxxxxxxx,,xxxxxx,xx,xxxxxx,xxxxxxxxxxxxxxxxxxxx,
y,888888,429,,,,,,,,,,,,,,,,,,,,8888888,,xxxxxxxx xxxxxxxx,,xxxxxxxx xxxxxxxx xxxxxxxx xxxxxxxx,,xxxxxxxx,xxxxxxxx,xxxxxxxx,,,,,
z,777777,429,,,,,,,,,,,,,,,,,,,,6666666,xxxxxxxx,xxxxxxxx xxxxxxxx,,xxxxxxxx xxxxxxxx xxxxxxxx xxxxxxxx,,xxxxxxxx,xxxxxxxx,xxxxxxxx
A,666666,429,,,,,,,,,,,,,,,,,,,,4444444,,xxxxxxxx xxxxxxxx,,xxxxxxxx xxxxxxxx,,xxxxxxxx,xxxxxxxx,xxxxxxxx,,,,,xxxxxxxx 
B,555555,429,,,,,,,,,,,,,,,,,,,,3333333,,xxxxxxxx xxxxxxxx,,xxxxxxxx xxxxxxxx xxxxxxxx,,xxxxxxxx,
C,444444,429,,,,,,,,,,,,,,,,,,,,2222222,,xxxxxxxx xxxxxxxx,,xxxxxxxx xxxxxxxx xxxxxxxx,,xxxxxxxx xxxxxxxx,
D,333333,429,,,,,,,,,,,,,,,,,,,,5555555,,xxxxxxxx xxxxxxxx,,xxxxxxxx xxxxxxxx xxxxxxxx

awk -F, '{ T=0; for(N=4; N<=22; N++) if($N) T++ } !T' inputfile

sed -n '/\([,]*,\)\{3\},\{17\}/p' file

sed -rn '/([,]*,){3},{17}/p' file