Linux 大檔案如何切割與合并？

往往是因為網絡傳輸的限制，導緻很多時候，我們需要在 Linux 系統下進行大檔案的切割。這樣将一個大檔案切割成為多個小檔案，進行傳輸，傳輸完畢之後進行合并即可。

Linux 大檔案的分割與合并

Linux 學習–檔案分割與合并

Linux下大檔案切割與合并

1. 檔案切割 - split

在 Linux 系統下使用 split 指令進行大檔案切割很友善

[1] 指令文法

# -a: 指定輸出檔案名的字尾長度(預設為2個:aa,ab...)
# -d: 指定輸出檔案名的字尾用數字代替
# -l: 行數分割模式(指定每多少行切成一個小檔案;預設行數是1000行)
# -b: 二進制分割模式(支援機關:k/m)
# -C: 檔案大小分割模式(切割時盡量維持每行的完整性)
split [-a] [-d] [-l <行數>] [-b <位元組>] [-C <位元組>] [要切割的檔案] [輸出檔案名]      

[2] 使用執行個體

# 行切割檔案
$ split -l 300000 users.sql /data/users_

# 使用數字字尾
$ split -d -l 300000 users.sql /data/users_

# 按位元組大小分割
$ split -d -b 100m users.sql /data/users_      

[3] 幫助資訊

# 幫助資訊
$ split --help
Usage: split [OPTION]... [FILE [PREFIX]]
Output pieces of FILE to PREFIXaa, PREFIXab, ...;
default size is 1000 lines, and default PREFIX is 'x'.

With no FILE, or when FILE 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)            字尾名稱的長度(預設為2)
      --additional-suffix=SUFFIX  append an additional SUFFIX to file names
  -b, --bytes=SIZE        put SIZE bytes per output file                       每個輸出檔案的位元組大小
  -C, --line-bytes=SIZE   put at most SIZE bytes of records per output file    每個輸出檔案的最大位元組大小
  -d                      use numeric suffixes starting at 0, not alphabetic   使用數字字尾代替字母字尾
      --numeric-suffixes[=FROM]  same as -d, but allow setting the start value
  -e, --elide-empty-files  do not generate empty output files with '-n'        不産生空的輸出檔案
      --filter=COMMAND    write to shell COMMAND; file name is $FILE           寫入到shell指令行
  -l, --lines=NUMBER      put NUMBER lines/records per output file             設定每個輸出檔案的行數
  -n, --number=CHUNKS     generate CHUNKS output files; see explanation below  産生chunks檔案
  -t, --separator=SEP     use SEP instead of newline as the record separator;  使用新字元分割
                            '\0' (zero) specifies the NUL character
  -u, --unbuffered        immediately copy input to output with '-n r/...'     無需緩存
      --verbose           print a diagnostic just before each                  顯示分割進度
                            output file is opened
      --help     display this help and exit                                    顯示幫助資訊
      --version  output version information and exit                           顯示版本資訊

The SIZE argument is an integer and optional unit (example: 10K is 10*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/records
  l/K/N   output Kth of N to stdout without splitting lines/records
  r/N     like 'l' but use round robin distribution
  r/K/N   likewise but only output Kth of N to stdout

GNU coreutils online help: <http://www.gnu.org/software/coreutils/>
Full documentation at: <http://www.gnu.org/software/coreutils/split>
or available locally via: info '(coreutils) split invocation'      

2. 檔案合并 - cat

在 Linux 系統下使用 cat 指令進行多個小檔案的合并也很友善

# -n: 顯示行号
# -e: 以$字元作為每行的結尾
# -t: 顯示TAB字元(^I)
cat [-n] [-e] [-t] [輸出檔案名]      

# 合并檔案
$ cat /data/users_* > users.sql      

# 幫助資訊
$ cat --h
Usage: cat [OPTION]... [FILE]...
Concatenate FILE(s) to standard output.

With no FILE, or when FILE is -, read standard input.

  -A, --show-all           equivalent to -vET
  -b, --number-nonblank    number nonempty output lines, overrides -n
  -e                       equivalent to -vE
  -E, --show-ends          display $ at end of each line
  -n, --number             number all output lines
  -s, --squeeze-blank      suppress repeated empty output lines
  -t                       equivalent to -vT
  -T, --show-tabs          display TAB characters as ^I
  -u                       (ignored)
  -v, --show-nonprinting   use ^ and M- notation, except for LFD and TAB
      --help     display this help and exit
      --version  output version information and exit

Examples:
  cat f - g  Output f's contents, then standard input, then g's contents.
  cat        Copy standard input to standard output.

GNU coreutils online help: <http://www.gnu.org/software/coreutils/>
Full documentation at: <http://www.gnu.org/software/coreutils/cat>
or available locally via: info '(coreutils) cat invocation'