csplit : Split a file based on patterns

The command "csplit" can be used to split a file into different files based on certain pattern in the file or line numbers.

For example let us say we have the file, temp, with the following contents

temp:

Line one Line two Line three Line four Line five Line six Line seven Line eight

we can split the file into two new files ,each having part of the contents of the original file, using csplit.

The syntax of csplit is

csplit [options] file PATTERN

Pattern as integer number:

When the pattern is an integer number it makes cplit to copy line upto that line number,no including the line, into a new file and contents after that into a new file.

Example:

$ csplit temp 5 40 42 $ ls temp xx00 xx01

The numbers printed after the command is executed is the number of bytes written into each new file that got created. After the execution of the command we can see that we have two new files "xx00" and "xx01", these are the files created by csplit.

$ cat xx00 Line one Line two Line three Line four $ cat xx01 Line five Line six Line seven Line eight

By looking at the contents of xx00 and xx01 we can observe that csplit has split the first 4 lines of file temp into one file and lines 5 till end of temp to another file .

The names of the new files created are by default of the format "xx00", "xx01"... etc.

Pattern as a Regular expression:

We can also pass regular expressions as patterns to split the file.

Example

$ csplit temp /two/ 9 73 $ ls temp xx00 xx01

We have passed the pattern as the string "two", which means we want to split the file temp at the first occurrence of the the string two.

$ cat xx00 Line one $ cat xx01 Line two Line three Line four Line five Line six Line seven Line eight

As we can see, the file xx00 only has the first line which is before the line containing the string "two" .

Repeating a pattern:

A pattern can be made to repeat any number of times by passing the integer after the pattern with in {} i.e

cplit [options] file PATTERN {integer}

csplit will then split the original file into integer number of new files, if the pattern repeats integer number of times else it will split maximum number of times possible which is less than the integer passed.

Examples:

$ csplit temp 1 {7} 0 9 10 11 10 10 9 11 12 $ ls temp xx00 xx01 xx02 xx03 xx04 xx05 xx06 xx07 xx08

In the above command we passed "1" as the pattern and 7 as integer for repeat. Thus the file was split 7 times with one line in each file.
The repetition can be made to occur as many times as possible by passing "*" instead of a number.

Example:

$ csplit temp /Line/ {*} 0 9 10 11 10 10 9 11 12 $ ls temp xx00 xx01 xx02 xx03 xx04 xx05 xx06 xx07 xx08

The above command split the file temp into a new file on each occurrence of the string /Line/ .

The output file prefix can be changed by using the option -f

$ csplit -f file temp 5 40 42 $ls file00 file01 temp

As we can see what ever string is passed after -f will be used as the prefix.
The number of digits used in the suffix can be changed using the option -n

$ csplit -f file -n 1 temp 5 40 42 $ ls file0 file1 temp

As we can see the number of digits after prefix "file" is only one, which was passed with the option "-n".