These docs are under active development and cover the v0.20 Kobicha security model.
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csplit

csplit — "context split" — breaks a file into pieces at points you choose: a line number, or a line that matches a pattern. Where split cuts a file into equal sizes, csplit cuts it at meaningful boundaries.

csplit [options] file pattern...

$ csplit report.txt '/^Chapter/' '{*}'

That splits report.txt into one piece per chapter, cutting at every line beginning with Chapter. The pieces are written to xx00, xx01, xx02, … and csplit prints the byte size of each.

Patterns

Each pattern argument marks a cut point. csplit copies everything up to that point into the next output file, then continues.

Pattern Cut where…
N (a number) line N is reached — the piece is lines up to N-1.
/REGEX/ a line matches REGEX; that line starts the next piece.
%REGEX% a line matches REGEX — but skip the text up to it instead of writing it to a piece.
/REGEX/+N or /REGEX/-N an offset of N lines from the matching line.
{N} repeat the previous pattern N more times.
{*} repeat the previous pattern as many times as the file allows.

A pattern that finds no match is an error, and by default csplit removes the pieces it had already written. -k keeps them.

Naming the pieces

Option Effect
-f, --prefix=PREFIX Use PREFIX instead of xx at the start of each output name.
-n, --digits=N Use N digits in the numeric part of the name instead of 2.
-b, --suffix-format=FORMAT Use a custom printf-style FORMAT for the numeric suffix.

Other options

Option Effect
-k, --keep-files Do not delete the output files if csplit fails partway.
-z, --elide-empty-files Do not write out pieces that would be empty.
--suppress-matched Drop the lines that the patterns matched, rather than keeping them in a piece.
-s, --quiet Do not print the byte size of each piece.

Exit status

Code Meaning
0 The file was split.
1 A pattern did not match, a line number was out of range, or the input could not be read.

See also