split is a Unix utility most commonly used to split a file into two or more smaller files.

# To split a file, each split having 10 lines (except the last split):
split -l <10> <filename>

# To split a file into 5 files. File is split such that each split has same size (except the last split):
split -n <5> <filename>

# To split a file with 512 bytes in each split (except the last split; use 512k for kilobytes and 512m for megabytes):
split -b <512> <filename>

# To split a file with at most 512 bytes in each split without breaking lines:
split -C <512> <filename>