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pt-fifo-split - Split files and pipe lines to a fifo without really splitting.



pt-fifo-split [OPTIONS] [FILE]

pt-fifo-split splits FILE and pipes lines to a fifo. With no FILE, or when FILE is -, read standard input.

Read hugefile.txt in chunks of a million lines without physically splitting it:

pt-fifo-split --lines 1000000 hugefile.txt
while [ -e /tmp/pt-fifo-split ]; do cat /tmp/pt-fifo-split; done


Percona Toolkit is mature, proven in the real world, and well tested, but all database tools can pose a risk to the system and the database server. Before using this tool, please:

  • Read the tool’s documentation

  • Review the tool’s known “BUGS”

  • Test the tool on a non-production server

  • Backup your production server and verify the backups


pt-fifo-split lets you read from a file as though it contains only some of the lines in the file. When you read from it again, it contains the next set of lines; when you have gone all the way through it, the file disappears. This works only on Unix-like operating systems.

You can specify multiple files on the command line. If you don’t specify any, or if you use the special filename -, lines are read from standard input.


This tool accepts additional command-line arguments. Refer to the “SYNOPSIS” and usage information for details.


type: Array

Read this comma-separated list of config files; if specified, this must be the first option on the command line.


type: string; default: /tmp/pt-fifo-split

The name of the fifo from which the lines can be read.


Remove the fifo if it exists already, then create it again.


Show help and exit.


type: int; default: 1000

The number of lines to read in each chunk.


type: int; default: 0

Begin at the Nth line. If the argument is 0, all lines are printed to the fifo. If 1, then beginning at the first line, lines are printed (exactly the same as 0). If 2, the first line is skipped, and the 2nd and subsequent lines are printed to the fifo.


type: string

Create the given PID file. The tool won’t start if the PID file already exists and the PID it contains is different than the current PID. However, if the PID file exists and the PID it contains is no longer running, the tool will overwrite the PID file with the current PID. The PID file is removed automatically when the tool exits.


Print out statistics between chunks. The statistics are the number of chunks, the number of lines, elapsed time, and lines per second overall and during the last chunk.


Show version and exit.


The environment variable PTDEBUG enables verbose debugging output to STDERR. To enable debugging and capture all output to a file, run the tool like:

PTDEBUG=1 pt-fifo-split ... > FILE 2>&1

Be careful: debugging output is voluminous and can generate several megabytes of output.


Using <PTDEBUG> might expose passwords. When debug is enabled, all command line parameters are shown in the output.


You need Perl, DBI, DBD::mysql, and some core packages that ought to be installed in any reasonably new version of Perl.


For a list of known bugs, see

Please report bugs at Include the following information in your bug report:

  • Complete command-line used to run the tool

  • Tool --version

  • MySQL version of all servers involved

  • Output from the tool including STDERR

  • Input files (log/dump/config files, etc.)

If possible, include debugging output by running the tool with PTDEBUG; see “ENVIRONMENT”.


Visit to download the latest release of Percona Toolkit. Or, get the latest release from the command line:




You can also get individual tools from the latest release:


Replace TOOL with the name of any tool.


Baron Schwartz


This tool is part of Percona Toolkit, a collection of advanced command-line tools for MySQL developed by Percona. Percona Toolkit was forked from two projects in June, 2011: Maatkit and Aspersa. Those projects were created by Baron Schwartz and primarily developed by him and Daniel Nichter. Visit to learn about other free, open-source software from Percona.


pt-fifo-split 3.5.7