Detailed explanation of using split command to split Linux files

A few simple Linux commands let you split and reassemble files as needed to fit within storage or email attachment size limitations.

The Linux system provides a very easy-to-use command to split files. You may want to do this before uploading a file to a storage site that limits the size of the file or before attaching it to an email. To split a file into multiple file chunks, just use the split command.

$ split bigfile

By default, the split command uses a very simple naming scheme. The file chunks will be named xaa, xab, xac, etc., and, presumably, if you split a large enough file, you might even get chunks named xza and xzz.

This command will run without any feedback unless you ask it to. However, if you want to see feedback as the file chunks are created, use the --verbose option.

$ split –-verbose bigfile
creating file 'xaa'
creating file 'xab'
creating file 'xac'

You can also give the files a name prefix. For example, to split your original file and name it bigfile.aa, bigfile.ab, etc., you can add the prefix to the end of the split command, like this:

$ split –-verbose bigfile bigfile.
creating file 'bigfile.aa'
creating file 'bigfile.ab'
creating file 'bigfile.ac'

Note that a dot is added to the end of the prefix shown in the above command. Otherwise, the file will be named something like bigfileaa instead of bigfile.aa.

Please note that the split command does not delete your original file, it just creates chunks of it. If you want to specify the file block size, you can add it to the command using the -b option. For example:

$ split -b100M bigfile

The file size can be KB, MB, GB, and the maximum can be YB! Just use the appropriate letters K, M, G, T, P, E, Z, and Y.

If you want to split the file based on the number of lines in each block rather than the number of bytes, you can use the -l (lines) option. In this example, each file will have 1000 lines, although the last file may have fewer lines.

$ split --verbose -l1000 logfile log.
creating file 'log.aa'
creating file 'log.ab'
creating file 'log.ac'
creating file 'log.ad'
creating file 'log.ae'
creating file 'log.af'
creating file 'log.ag'
creating file 'log.ah'
creating file 'log.ai'
creating file 'log.aj'

If you need to reassemble the files on the remote site, you can easily do this using the cat command as follows:

$ cat x?? > original.file
$ cat log.?? > original.file

The split and combine commands shown above are suitable for both binary and text files. In this example, we split the zip binary file into 50KB chunks, then reassembled them using cat, and then compared the reassembled file with the original file. The diff command verifies that files are identical.

$ split --verbose -b50K zip zip.
creating file 'zip.aa'
creating file 'zip.ab'
creating file 'zip.ac'
creating file 'zip.ad'
creating file 'zip.ae'
$ cat zip.a? > zip.new
$ diff zip zip.new
$ <== no output = no difference

The only thing I would caution is that if you use split a lot and use the default naming, some chunks may overwrite other chunks, even more than you expected, because some were split earlier.

Summarize

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