Uses Shell command split
# split file according to line count
split -l <line count> <file>
# split file according to segment size
split -b <size|ex.512m for 0.5GB segments> <file>
# split by RegEx, every segment would start with a match (maybe not for 1st segment)
split -p <RegEx> <file>
touch combined.ext
cat seg_aa > combined.ext
cat seg_ab >> combined.ext
cat seg_ac >> combined.ext
#...
Sources: