split a 10meg file named 10M into 10MSpliteda .... 10MSplitedk, each 1024000 bytes

$ split -b 1024000 10M 10MSplited

make a single file out of the splitted files

$ cat 10MSpliteda 10MSplitedb 10MSplitedc 10MSplitedd 10MSplitede 10MSplitedf 10MSplitedg 10MSplitedh 10MSplitedi 10MSplitedj 10MSplitedk >> 10M2