split(s,a)                   split string

    Split string s into  array a on field  separator FS.  Return  number of
    fields.

split(s,a,fs)                split string

    Split string s into  array a on field  separator fs.  Return  number of
    fields.

    split("This string contains five fields.",astr)

    astr[1] == This
    astr[2] == string
    astr[3] == contains
    astr[4] == five
    astr[5] == fields.