csplit - macOS


The csplit command in macOS is used to split files into sections determined by context lines. This tool is especially useful for processing logs, data files, or any large file that needs to be broken down into manageable parts based on content patterns.


csplit [options] file pattern...
  • file specifies the input file to split.
  • pattern defines where to split the file. It can be a line number, a regular expression, or any combination of these.


  • -f, --prefix=PREFIX: Prefix of file names to create, default is xx.
  • -b, --suffix-format=FORMAT: Format of the file suffix (default is %02d), where %d indicates decimal numbers.
  • -n, --digits=DIGITS: Use DIGITS digits to form file names.
  • -k, --keep-files: Do not remove output files on errors.
  • -s, --quiet, --silent: Suppress all normal output.
  • -z, --elide-empty-files: Do not create files that would be empty.
  • -h, --help: Display help message and exit.


  1. Splitting a file at a specific line number:

    csplit file.txt 10

    This splits file.txt, creating a new file with the first 9 lines, and another with the rest.

  2. Using regular expressions:

    csplit file.txt /pattern/

    This command splits file.txt at every line containing pattern.

  3. Advanced splitting with multiple patterns and custom file names:

    csplit -f output -b "%03d.txt" file.txt 20 /pattern/ {*}

    Splits file.txt at line 20, every occurrence of pattern, and all subsequent matches, using custom filenames like output000.txt.

Common Issues

  • Pattern not found: If csplit does not find the pattern, it exits with an error. Ensure the pattern exists in the file or use a more general pattern.
  • Permission denied: Happens when csplit does not have the rights to read the input file or write outputs. Check and modify the file permissions.


Combine csplit with other commands to handle complex text processing tasks:

csplit largefile.log /ERROR/ {*} && grep 'SpecificError' xx* | less

This sequence splits largefile.log at each occurrence of ERROR, then greps for SpecificError in each split file, displaying the results in a paginated format.

  • split: Splits a file into pieces based on size rather than content.
  • grep: Searches text and can be used to determine the patterns for csplit.
  • awk: Another text-processing tool that can be used for more complex splitting logic.

For further reading, consult the csplit man page with man csplit on your macOS terminal or visit the official GNU documentation online.