map/reduce in bash
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NAME br - bashreduce, map/reduce in bash SYNOPSIS br [-h '<host>[ <host>][...]'] [-f] [-m <map>] [-r <reduce>] [-M <merge>] [-i <input>] [-o <output>] [-c <column>] [-S <sort-mem-MB>] [-t <tmp>] [-?] DESCRIPTION br implements a map/reduce framework that allows the map and reduce jobs to be constructed from standard Unix tools. It can operate on data piped into it or on files known to exist on the worker nodes. INSTALLATION br can run out-of-the box but for convenience, put it somewhere on your PATH. The brutils come with a Makefile that will install these tools, probably to /usr/local/bin. If you leave these tools in place relative to br, they'll be picked up and used from there. You'll need passwordless ssh access to each machine you wish to use as a worker (even localhost, for now). OPTIONS -h The list of hosts to be used, specified as a space- delimited list. Specifying the same host multiple times is allowed and is useful for taking explicit advantage of multiple cores. -f Only pass filenames from the master to the workers, under the assumption that they all have a mirror of the data set. This is equivalent to prefixing your map program with "xargs cat |". -m The map program, which should expect initial data on stdin and produce the intermediate data on stdout. The stderr from this program will be logged . -r The reduce program, which should expect intermediate data on stdin and produce the final data on stdout. The stderr from this program will be logged . -M The merge program, which should expect each node's final data on stdin and produce the unified final data on stdout. The stderr from this program will be logged . -i A file or directory to serve as input. If it is a file, this is equivalent to piping that file into br. If it is a directory, it is equivalent to piping the names of every file in that directory into br. -o The local file where output will be stored. Defaults to stdout. -c The column used by sort to produce the final output. Defaults to 1. -S This is directly the -S option from sort(1). It defaults to 256M. -t The temporary directory for storing br files. All of these files will be prefixed with "br_" and, with the exception of br_stderr, will be cleaned up upon successful exit. Defaults to /tmp. -? Shows a help message and details about the arguments. FILES All of these files are in the tmp directory specified by the user, which defaults to /tmp. br_job_* The master uses named pipes to move data (or filenames) to the worker(s). These pipes are stored here. This directory is removed at the end of the job. br_node_* Each node uses named pipes to buffer data. These are stored here and do not overlap, even if a node is specified twice in the host list. These directories are removed at the end of the job. br_stderr This file is cleared at the beginning of each job. It records stderr from most commands run by br. This is currently a point of contention between jobs. This file is NOT removed at the end of the job. NOTES  Because you can specify a pipeline for any or all of the map, reduce and merge steps, br can only reliably log stderr from the last step in those pipelines. AUTHORS Erik Frey <email@example.com> Richard Crowley <firstname.lastname@example.org> SEE ALSO <http://github.com/erikfrey/bashreduce> <http://github.com/rcrowley/bashreduce> LICENSE The goodwill of Erik Frey.