文字列内の最初のトークンを出力

strtok

token = strtok('str',delimiter);

s = 'This is a book, which I gave you.';
[token1,rem1] = strtok(s,',');
token1 = This is a book
[token2,rem2] = strtok(s,'.');
token2 = This is a book, which I gave you