int sscanf(str, fmt, var1, var2 ...)
string str;
string fmt;

Parse a string "str" using the format "fmt". "fmt" can contain strings
separated by "%d" and "%s". Every "%d" and "%s" corresponds to one
of var1, var2...
"%d" will give a number, and "%s" will give a string.

Number of matched "%d" and "%s" is returned.

See also input_to().