split is as specified in the Single UNIX Specification but with differences as listed below.
has unspecified behavior. 
The behaviors specified in this section are expected to disappear from a future version of the LSB; applications should only use the non-LSB-deprecated behaviors.
is equivalent to -b.
puts at most SIZE bytes of lines per output file.
is equivalent to -l.
prints a diagnostic to standard error.
outputs version information and exits.
Newer versions of split in GNU textutils have support for the -a flag. In a future version of the LSB, the -a flag will be required to conform to the Single UNIX Specification definition.