5.4 csplit: Split a file into context-determined pieces

csplit creates zero or more output files containing sections of input (standard input if input is ‘-’). Synopsis:

csplit [option]… input pattern

The contents of the output files are determined by the pattern arguments, as detailed below. An error occurs if a pattern argument refers to a nonexistent line of the input file (e.g., if no remaining line matches a given regular expression). After every pattern has been matched, any remaining input is copied into one last output file.

By default, csplit prints the number of bytes written to each output file after it has been created.

The types of pattern arguments are:


Create an output file containing the input up to but not including line n (a positive integer). If followed by a repeat count, also create an output file containing the next n lines of the input file once for each repeat.


Create an output file containing the current line up to (but not including) the next line of the input file that contains a match for regexp. The optional offset is an integer, that can be preceded by ‘+’ or ‘-’. If it is given, the input up to (but not including) the matching line plus or minus offset is put into the output file, and the line after that begins the next section of input. Lines within a negative offset of a regexp pattern are not matched in subsequent regexp patterns.


Like the previous type, except that it does not create an output file, so that section of the input file is effectively ignored.


Repeat the previous pattern repeat-count additional times. The repeat-count can either be a positive integer or an asterisk, meaning repeat as many times as necessary until the input is exhausted.

The output files’ names consist of a prefix (‘xx’ by default) followed by a suffix. By default, the suffix is an ascending sequence of two-digit decimal numbers from ‘00’ to ‘99’. In any case, concatenating the output files in sorted order by file name produces the original input file, excluding portions skipped with a %regexp% pattern or the --suppress-matched option.

By default, if csplit encounters an error or receives a hangup, interrupt, quit, or terminate signal, it removes any output files that it has created so far before it exits.

The program accepts the following options. Also see Common options.

-f prefix

Use prefix as the output file name prefix.

-b format

Use format as the output file name suffix. When this option is specified, the suffix string must include exactly one printf(3)-style conversion specification, possibly including format specification flags, a field width, a precision specification, or all of these kinds of modifiers. The format letter must convert a binary unsigned integer argument to readable form. The format letters ‘d’ and ‘i’ are aliases for ‘u’, and the ‘u’, ‘o’, ‘x’, and ‘X’ conversions are allowed. The entire format is given (with the current output file number) to sprintf(3) to form the file name suffixes for each of the individual output files in turn. If this option is used, the --digits option is ignored.

-n digits

Use output file names containing numbers that are digits digits long instead of the default 2.


Do not remove output files when errors are encountered.


Do not output lines matching the specified pattern. I.e., suppress the boundary line from the start of the second and subsequent splits.


Suppress the generation of zero-length output files. (In cases where the section delimiters of the input file are supposed to mark the first lines of each of the sections, the first output file will generally be a zero-length file unless you use this option.) The output file sequence numbers always run consecutively starting from 0, even when this option is specified.


Do not print counts of output file sizes.

An exit status of zero indicates success, and a nonzero value indicates failure.

Here is an example of its usage. First, create an empty directory for the exercise, and cd into it:

$ mkdir d && cd d

Now, split the sequence of 1..14 on lines that end with 0 or 5:

$ seq 14 | csplit - '/[05]$/' '{*}'

Each number printed above is the size of an output file that csplit has just created. List the names of those output files:

$ ls
xx00  xx01  xx02

Use head to show their contents:

$ head xx*
==> xx00 <==

==> xx01 <==

==> xx02 <==

Example of splitting input by empty lines:

$ csplit --suppress-matched input.txt '/^$/' '{*}'