The string functions are particularly useful as template modifiers.
cut
Cut a string and add "..." at the end of it.
{$string|cut:10} // output Hello Worl...
cut_html
Cut an html string and add "..." at the end of it. It can remove html tags and images, and it mantain the html valid.
{$value.news|cut_html:30} // output New version of Rain Framewor...
rand_str( length )
Return a random string
rand_str( 5 ); // 9Ay6W random string