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 cuts report.txt at every line beginning with Chapter, including an initial piece before the first match. That initial piece is empty if the first line matches. The pieces are written to xx00, xx01, xx02, … and csplit prints the byte size of each.
Each piece is a newly created file, and a new file needs a security descriptor; each piece inherits one from the directory it is created in.
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. |