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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 .
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