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PROLOG
This manual page is part of the POSIX Programmer's Manual. The Linux implementation of this interface
may differ (consult the corresponding Linux manual page for details of Linux behavior), or the interface
may not be implemented on Linux.
NAME
csplit — split files based on context
SYNOPSIS
csplit [-ks] [-f prefix] [-n number] file arg...
DESCRIPTION
The csplit utility shall read the file named by the file operand, write all or part of that file into
other files as directed by the arg operands, and write the sizes of the files.
OPTIONS
The csplit utility shall conform to the Base Definitions volume of POSIX.1‐2017, Section 12.2, Utility
Syntax Guidelines.
The following options shall be supported:
-f prefix Name the created files prefix00, prefix01, ..., prefixn. The default is xx00 ... xxn. If the
prefix argument would create a filename exceeding {NAME_MAX} bytes, an error shall result,
csplit shall exit with a diagnostic message, and no files shall be created.
-k Leave previously created files intact. By default, csplit shall remove created files if an
error occurs.
-n number Use number decimal digits to form filenames for the file pieces. The default shall be 2.
-s Suppress the output of file size messages.
OPERANDS
The following operands shall be supported:
file The pathname of a text file to be split. If file is '-', the standard input shall be used.
Each arg operand can be one of the following:
/rexp/[offset]
A file shall be created using the content of the lines from the current line up to, but not
including, the line that results from the evaluation of the regular expression with offset, if
any, applied. The regular expression rexp shall follow the rules for basic regular expressions
described in the Base Definitions volume of POSIX.1‐2017, Section 9.3, Basic Regular
Expressions. The application shall use the sequence "\/" to specify a <slash> character within
the rexp. The optional offset shall be a positive or negative integer value representing a
number of lines. A positive integer value can be preceded by '+'. If the selection of lines
from an offset expression of this type would create a file with zero lines, or one with greater
than the number of lines left in the input file, the results are unspecified. After the section
is created, the current line shall be set to the line that results from the evaluation of the
regular expression with any offset applied. If the current line is the first line in the file
and a regular expression operation has not yet been performed, the pattern match of rexp shall
be applied from the current line to the end of the file. Otherwise, the pattern match of rexp
shall be applied from the line following the current line to the end of the file.
%rexp%[offset]
Equivalent to /rexp/[offset], except that no file shall be created for the selected section of
the input file. The application shall use the sequence "\%" to specify a <percent-sign>
character within the rexp.
line_no Create a file from the current line up to (but not including) the line number line_no. Lines
in the file shall be numbered starting at one. The current line becomes line_no.
{num} Repeat operand. This operand can follow any of the operands described previously. If it follows
a rexp type operand, that operand shall be applied num more times. If it follows a line_no
operand, the file shall be split every line_no lines, num times, from that point.
An error shall be reported if an operand does not reference a line between the current position and the
end of the file.
STDIN
See the INPUT FILES section.
INPUT FILES
The input file shall be a text file.
ENVIRONMENT VARIABLES
The following environment variables shall affect the execution of csplit:
LANG Provide a default value for the internationalization variables that are unset or null. (See the
Base Definitions volume of POSIX.1‐2017, Section 8.2, Internationalization Variables for the
precedence of internationalization variables used to determine the values of locale
categories.)
LC_ALL If set to a non-empty string value, override the values of all the other internationalization
variables.
LC_COLLATE
Determine the locale for the behavior of ranges, equivalence classes, and multi-character
collating elements within regular expressions.
LC_CTYPE 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) and
the behavior of character classes within regular expressions.
LC_MESSAGES
Determine the locale that should be used to affect the format and contents of diagnostic
messages written to standard error.
NLSPATH Determine the location of message catalogs for the processing of LC_MESSAGES.
ASYNCHRONOUS EVENTS
If the -k option is specified, created files shall be retained. Otherwise, the default action occurs.
STDOUT
Unless the -s option is used, the standard output shall consist of one line per file created, with a
format as follows:
"%d\n", <file size in bytes>
STDERR
The standard error shall be used only for diagnostic messages.
OUTPUT FILES
The output files shall contain portions of the original input file; otherwise, unchanged.
EXTENDED DESCRIPTION
None.
EXIT STATUS
The following exit values shall be returned:
0 Successful completion.
>0 An error occurred.
CONSEQUENCES OF ERRORS
By default, created files shall be removed if an error occurs. When the -k option is specified, created
files shall not be removed if an error occurs.
The following sections are informative.
APPLICATION USAGE
None.
EXAMPLES
1. This example creates four files, cobol00 ... cobol03:
csplit -f cobol file '/procedure division/' /par5./ /par16./
After editing the split files, they can be recombined as follows:
cat cobol0[0-3] > file
Note that this example overwrites the original file.
2. This example would split the file after the first 99 lines, and every 100 lines thereafter, up to
9999 lines; this is because lines in the file are numbered from 1 rather than zero, for historical
reasons:
csplit -k file 100 {99}
3. Assuming that prog.c follows the C-language coding convention of ending routines with a '}' at the
beginning of the line, this example creates a file containing each separate C routine (up to 21) in
prog.c:
csplit -k prog.c '%main(%' '/^}/+1' {20}
RATIONALE
The -n option was added to extend the range of filenames that could be handled.
Consideration was given to adding a -a flag to use the alphabetic filename generation used by the
historical split utility, but the functionality added by the -n option was deemed to make alphabetic
naming unnecessary.
FUTURE DIRECTIONS
None.
SEE ALSO
sed, split
The Base Definitions volume of POSIX.1‐2017, Chapter 8, Environment Variables, Section 9.3, Basic Regular
Expressions, Section 12.2, Utility Syntax Guidelines
COPYRIGHT
Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1-2017, Standard
for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 7, 2018 Edition, Copyright (C) 2018 by the Institute of Electrical and Electronics
Engineers, Inc and The Open Group. In the event of any discrepancy between this version and the original
IEEE and The Open Group Standard, the original IEEE and The Open Group Standard is the referee document.
The original Standard can be obtained online at http://www.opengroup.org/unix/online.html .
Any typographical or formatting errors that appear in this page are most likely to have been introduced
during the conversion of the source files to man page format. To report such errors, see
https://www.kernel.org/doc/man-pages/reporting_bugs.html .
IEEE/The Open Group 2017 CSPLIT(1POSIX)