1.（实测）按行拆分txt文件 (将50,000,000行的dddd.txt文件拆成5个文件，每个文件10,000,000行)
split -l 10000000 dddd.txt aa（aa为拆分文件的前缀-可选）
2.其他可以参考如下内容(split –help查询到的内容)：
Usage: split [OPTION]… [INPUT [PREFIX]]
Output fixed-size pieces of INPUT to PREFIXaa, PREFIXab, …; default
size is 1000 lines, and default PREFIX is ‘x’. With no INPUT, or when INPUT
is -, read standard input.
Mandatory arguments to long options are mandatory for short options too.
-a, –suffix-length=N generate suffixes of length N (default 2)
–additional-suffix=SUFFIX append an additional SUFFIX to file names
-b, –bytes=SIZE put SIZE bytes per output file
-C, –line-bytes=SIZE put at most SIZE bytes of lines per output file
-d, –numeric-suffixes[=FROM] use numeric suffixes instead of alphabetic;
FROM changes the start value (default 0)
-e, –elide-empty-files do not generate empty output files with ‘-n’
–filter=COMMAND write to shell COMMAND; file name is $FILE
-l, –lines=NUMBER put NUMBER lines per output file
-n, –number=CHUNKS generate CHUNKS output files; see explanation below
-u, –unbuffered immediately copy input to output with ‘-n r/…’
–verbose print a diagnostic just before each
output file is opened
–help display this help and exit
–version output version information and exit
SIZE is an integer and optional unit (example: 10M is 10*1024*1024). Units
are K, M, G, T, P, E, Z, Y (powers of 1024) or KB, MB, … (powers of 1000).
CHUNKS may be:
N split into N files based on size of input
K/N output Kth of N to stdout
l/N split into N files without splitting lines
l/K/N output Kth of N to stdout without splitting lines
r/N like ‘l’ but use round robin distribution
r/K/N likewise but only output Kth of N to stdout
