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


Usage: 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


The following section is included to inform users about the potential risks, whether known or unknown, of using this tool. The two main categories of risks are those created by the nature of the tool (e.g. read-only tools vs. read-write tools) and those created by bugs.

pt-fifo-split creates and/or deletes the “–fifo” file. Otherwise, no other files are modified, and it merely reads lines from the file given on the command-line. It should be very low-risk.

At the time of this release, we know of no bugs that could cause serious harm to users.

The authoritative source for updated information is always the online issue tracking system. Issues that affect this tool will be marked as such. You can see a list of such issues at the following URL:

See also “BUGS” for more information on filing bugs and getting help.


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.

--force Remove the fifo if it exists already, then create it again.
--help 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 file contains the process ID of the script. The PID file is removed when the script exits. Before starting, the script checks if the PID file already exists. If it does not, then the script creates and writes its own PID to it. If it does, then the script checks the following: if the file contains a PID and a process is running with that PID, then the script dies; or, if there is no process running with that PID, then the script overwrites the file with its own PID and starts; else, if the file contains no PID, then the script dies.

--statistics 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.
--version 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.


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 developed by Percona for MySQL support and consulting. Percona Toolkit was forked from two projects in June, 2011: Maatkit and Aspersa. Those projects were created by Baron Schwartz and developed primarily by him and Daniel Nichter, both of whom are employed by Percona. Visit for more software developed by Percona.


pt-fifo-split 1.0.2

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