The Open Group Base Specifications Issue 6
IEEE Std 1003.1, 2004 Edition
Copyright © 2001-2004 The IEEE and The Open Group, All Rights reserved.


split - split files into pieces


[UP] [Option Start] split [-l line_count][-a suffix_length][file[name]]

split -b
n[k|m][-a suffix_length][file[name]][Option End]


The split utility shall read an input file and write one or more output files. The default size of each output file shall be 1000 lines. The size of the output files can be modified by specification of the -b or -l options. Each output file shall be created with a unique suffix. The suffix shall consist of exactly suffix_length lowercase letters from the POSIX locale. The letters of the suffix shall be used as if they were a base-26 digit system, with the first suffix to be created consisting of all 'a' characters, the second with a 'b' replacing the last 'a', and so on, until a name of all 'z' characters is created. By default, the names of the output files shall be 'x', followed by a two-character suffix from the character set as described above, starting with "aa", "ab", "ac", and so on, and continuing until the suffix "zz", for a maximum of 676 files.

If the number of files required exceeds the maximum allowed by the suffix length provided, such that the last allowable file would be larger than the requested size, the split utility shall fail after creating the last file with a valid suffix; split shall not delete the files it created with valid suffixes. If the file limit is not exceeded, the last file created shall contain the remainder of the input file, and may be smaller than the requested size.


The split utility shall conform to the Base Definitions volume of IEEE Std 1003.1-2001, Section 12.2, Utility Syntax Guidelines.

The following options shall be supported:

-a  suffix_length
Use suffix_length letters to form the suffix portion of the filenames of the split file. If -a is not specified, the default suffix length shall be two. If the sum of the name operand and the suffix_length option-argument would create a filename exceeding {NAME_MAX} bytes, an error shall result; split shall exit with a diagnostic message and no files shall be created.
-b  n
Split a file into pieces n bytes in size.
-b  nk
Split a file into pieces n*1024 bytes in size.
-b  nm
Split a file into pieces n*1048576 bytes in size.
-l  line_count
Specify the number of lines in each resulting file piece. The line_count argument is an unsigned decimal integer. The default is 1000. If the input does not end with a <newline>, the partial line shall be included in the last output file.


The following operands shall be supported:

The pathname of the ordinary file to be split. If no input file is given or file is '-', the standard input shall be used.
The prefix to be used for each of the files resulting from the split operation. If no name argument is given, 'x' shall be used as the prefix of the output files. The combined length of the basename of prefix and suffix_length cannot exceed {NAME_MAX} bytes. See the OPTIONS section.


See the INPUT FILES section.


Any file can be used as input.


The following environment variables shall affect the execution of split:

Provide a default value for the internationalization variables that are unset or null. (See the Base Definitions volume of IEEE Std 1003.1-2001, Section 8.2, Internationalization Variables for the precedence of internationalization variables used to determine the values of locale categories.)
If set to a non-empty string value, override the values of all the other internationalization variables.
Determine the locale for the interpretation of sequences of bytes of text data as characters (for example, single-byte as opposed to multi-byte characters in arguments and input files).
Determine the locale that should be used to affect the format and contents of diagnostic messages written to standard error.
[XSI] [Option Start] Determine the location of message catalogs for the processing of LC_MESSAGES . [Option End]




Not used.


The standard error shall be used only for diagnostic messages.


The output files contain portions of the original input file; otherwise, unchanged.




The following exit values shall be returned:

Successful completion.
An error occurred.



The following sections are informative.




In the following examples foo is a text file that contains 5000 lines.

  1. Create five files, xaa, xab, xac, xad, and xae:

    split foo
  2. Create five files, but the suffixed portion of the created files consists of three letters, xaaa, xaab, xaac, xaad, and xaae:

    split -a 3 foo
  3. Create three files with four-letter suffixes and a supplied prefix, bar_aaaa, bar_aaab, and bar_aaac:

    split -a 4 -l 2000 foo bar_
  4. Create as many files as are necessary to contain at most 20*1024 bytes, each with the default prefix of x and a five-letter suffix:

    split -a 5 -b 20k foo


The -b option was added to provide a mechanism for splitting files other than by lines. While most uses of the -b option are for transmitting files over networks, some believed it would have additional uses.

The -a option was added to overcome the limitation of being able to create only 676 files.

Consideration was given to deleting this utility, using the rationale that the functionality provided by this utility is available via the csplit utility (see csplit). Upon reconsideration of the purpose of the User Portability Extension, it was decided to retain both this utility and the csplit utility because users use both utilities and have historical expectations of their behavior. Furthermore, the splitting on byte boundaries in split cannot be duplicated with the historical csplit.

The text " split shall not delete the files it created with valid suffixes" would normally be assumed, but since the related utility, csplit, does delete files under some circumstances, the historical behavior of split is made explicit to avoid misinterpretation.






First released in Issue 2.

Issue 6

This utility is marked as part of the User Portability Utilities option.

The APPLICATION USAGE section is added.

The obsolescent SYNOPSIS is removed.

End of informative text.

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