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split command

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The external split  command splits a file into smaller files based on a specified number of lines or the size of the chunk. Each of those chunks are equal in size, with the exception of the last one. Each has unique suffixes (alphabetic (default) or numeric  -- your choice; numeric are specified by option -d). Your original file is not changed by split.

The split  command is absolutely necessary for dividing huge data file into more manageble chunks, for example for transmission

The original file can be recreated from chunks using cat command.

Since the extensions added by split  create chunks ascending order of filenames, you can process generated chunks using shell loop.

There are some commands that cannot handle extremely large files; therefore, you may have to split  the input for these commands into more manageable blocks. You may also wish to investigate the csplit command, which splits files based on context.

The split  command reads input from a file or the standard input and creates multiple output files. It can be used as the last stage of the pipeline.  General format:

The general format of the split  command follows.

     split [options] [file [prefix]

Each resulting chunk can contain either fixed amount of bites (-b) or lines (-l). The size abbreviations are K, M, G, T, P, E, Z, Y (powers of 1024), or KB, MB, GB, and so on for powers of 1000.

The size abbreviations are K, M, G, T, P, E, Z, Y (powers of 1024), or KB, MB, GB, and so on for powers of 1000.

If you provide the prefix argument, the destination files are named prefixXX. Where XX is aa for the first file, ab for the second, and continues until the file zz. That's a total of 676 files you can generate if you divide your input into small enough sizes. When using prefix, you must use a name two characters shorter than the maximum allowed for filenames. Maximum filename length is 100; therefore, you can only use filenames of 98 characters for prefix. If you do not provide a prefix argument, the destination files are named xXX. split  uses the x as a prefix.

The option -a allows  to specify the length of the suffix. by default suffix is alphabetical, but it canbe changed to numberical with the option -d

You can use both prefix and suffix for the filenames:
$ split -a 3 --numeric-suffixes=9 --additional-suffix=mine foo.mv SB
240K Aug 21 17:44 SB009mine
214K Aug 21 17:44 SB010mine
220K Aug 21 17:44 SB011mine

The -a controls how many numeric digits there are. --numeric-suffixes sets the starting point for numbering. The default prefix is x, and you can set a different prefix by typing it after the filename.

If you wanted to split files into roughly the same size, but preserve the line structure, you can use option -C. With -C, you can specify a maximum size. Then the program will automatically split the files based on complete lines into chunks equal of less the specified size.
 

Options

Mandatory arguments to long options are mandatory for short options too.
-a, --suffix-length=N
use suffixes of length N (default 2)
-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 
use numeric suffixes instead of alphabetic
-l, --lines=NUMBER
put NUMBER lines per output file
--verbose 
print a diagnostic to standard error just before each output file is opened
--help 
display this help and exit
--version 
output version information and exit

SIZE may have a multiplier suffix: b for 512, k for 1K, m for 1 Meg.

Arguments

The following list describes the arguments that may be passed to the split  command.

- Causes split  to read from the standard input.
file The name of the file split  reads and divides into n or 1000 line files.
If no file is given on the command line, split  will read from the standard input.
prefix The base part of the name used for all output files. An extension is added to prefix for each file created. The extension is made up of two alpha characters. The first file extension is "aa," then "ab," and so on until the original input is completely divided.
If prefix is not specified, the output is written to a file with a base part of "x" and the normal extensions. Thus the default output filenames are xaa, xab, and so on.

split  places its output in files with an extension of two characters. The characters begin with "aa," the next file is "ab," and so on until the entire input has been split and stored in multiple files.

Examples

In this activity you use the split  command to divide the standard input into separate output files. Begin at the shell prompt.

ls /bin | split -20 - bin

Generate exactly n chunks  with split command (option -n)

Letís suppose we want to split an iso file into 4 chunk output files. Use Ď-ní option with split command limit the number of split output files.

split -n5 linux-lite.iso

Here are some additional examples from 11 Useful split command examples for Linux-UNIX systems

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Prevent Zero Size Split output files with option (-e)

There can be some scenarios where we split a small file into a large number of chunk files and zero size split output files can be created in such cases, so to avoid zero size split output file, use the option Ď-eí

[root@linuxtechi ~]# split -n60 -e tuxlap.txt
[root@linuxtechi ~]# ls -l x*
-rw-r--r--. 1 root root 2000 Nov 11 05:34 xaa
-rw-r--r--. 1 root root 2000 Nov 11 05:34 xab
-rw-r--r--. 1 root root 2000 Nov 11 05:34 xac
-rw-r--r--. 1 root root 2000 Nov 11 05:34 xad
-rw-r--r--. 1 root root 2000 Nov 11 05:34 xae
-rw-r--r--. 1 root root 2000 Nov 11 05:34 xaf
-rw-r--r--. 1 root root 2000 Nov 11 05:34 xag
-rw-r--r--. 1 root root 2000 Nov 11 05:34 xah
.............
-rw-r--r--. 1 root root 2000 Nov 11 05:34 xce
-rw-r--r--. 1 root root 2000 Nov 11 05:34 xcf
-rw-r--r--. 1 root root 2000 Nov 11 05:34 xcg
-rw-r--r--. 1 root root 2010 Nov 11 05:34 xch
[root@linuxtechi ~]#

Example:9) Create Split output files of customize suffix length (-a option)

Letís suppose we want to split an iso file and where size of each split output file is 500MB and suffix length is to be 3.  Use the following split command:

[root@linuxtechi ~]# split -b 500M linux-lite.iso -a 3

[root@linuxtechi ~]# ll
total 2048124
-rw-------. 1 root root        980 Aug 12 00:11 anaconda-ks.cfg
-rwx------. 1 root root 1048576000 Nov 11 03:54 linux-lite.iso
-rw-r--r--. 1 root root     120010 Nov 11 04:39 tuxlap.txt
-rw-r--r--. 1 root root  524288000 Nov 11 05:43 xaaa
-rw-r--r--. 1 root root  524288000 Nov 11 05:43 xaab
[root@linuxtechi ~]#

Example: 10) Split ISO file and merge it into a single file.

Letís suppose we have a Windows Server ISO file of size 4.2 GB and we are unable to scp this file to remote server because of its size.

To resolve such type of issues we can split the ISO into n number of pieces and will copy these pieces to remote sever and on the remote server we can merge these pieces into a single file using cat command,

[root@linuxtechi ~]# split -b 800M Windows2012r2.iso Split_IS0_

View the split output files using ll command,

[root@linuxtechi ~]# ll
total 8871788
-rw-------. 1 root root        980 Aug 12 00:11 anaconda-ks.cfg
-rw-r--r--. 1 root root  838860800 Nov 11 06:29 Split_IS0_aa
-rw-r--r--. 1 root root  838860800 Nov 11 06:29 Split_IS0_ab
-rw-r--r--. 1 root root  838860800 Nov 11 06:29 Split_IS0_ac
-rw-r--r--. 1 root root  838860800 Nov 11 06:29 Split_IS0_ad
-rw-r--r--. 1 root root  838860800 Nov 11 06:29 Split_IS0_ae
-rw-r--r--. 1 root root  347987968 Nov 11 06:29 Split_IS0_af
-rw-r--r--. 1 root root     120010 Nov 11 04:39 tuxlap.txt
-rwx------. 1 root root 4542291968 Nov 11 06:03 Windows2012r2.iso
[root@linuxtechi ~]#

Now scp these files to remote server and merge these files into a single using cat command

[root@linuxtechi ~]# cat Split_IS0_a* > Windows_Server.iso
[root@linuxtechi ~]#

Example: 11) Verify the Integrity of Merge file using md5sum utility

As per Example 10, once the split output files are merged into a single file, then we can check the integrity of actual & merge file with md5sum utility. Example is shown below:

[root@linuxtechi ~]# md5sum Windows2012r2.iso
5b5e08c490ad16b59b1d9fab0def883a  Windows2012r2.iso
[root@linuxtechi ~]#

[root@linuxtechi ~]# md5sum Windows_Server.iso
5b5e08c490ad16b59b1d9fab0def883a  Windows_Server.iso
[root@linuxtechi ~]#

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