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Full Discussion: How to make parallel execution on folder ?
Top Forums Shell Programming and Scripting How to make parallel execution on folder ? Post 302922775 by drl on Tuesday 28th of October 2014 08:48:19 AM
Old 10-28-2014
Hi.

One technique for parallelizing processing on large files is to use GNU parallel. If you are interested in re-arranging the order of fields in a file, say with cut or awk, then parallel can create a sequence of processes to do this in chunks.

Here's an example from the man page:
Code:
EXAMPLE: Processing a big file using more cores
       To process a big file or some output you can use --pipe to split up the
       data into blocks and pipe the blocks into the processing program.

       If the program is gzip -9 you can do:

       cat bigfile | parallel --pipe --recend '' -k gzip -9 >bigfile.gz

       This will split bigfile into blocks of 1 MB and pass that to gzip -9 in
       parallel. One gzip will be run per CPU core. The output of gzip -9 will
       be kept in order and saved to bigfile.gz

       gzip works fine if the output is appended, but some processing does not
       work like that - for example sorting. For this GNU parallel can put the
       output of each command into a file. This will sort a big file in
       parallel:

       cat bigfile | parallel --pipe --files sort | parallel -Xj1 sort -m {}
       ';' rm {} >bigfile.sort

       Here bigfile is split into blocks of around 1MB, each block ending in
       '\n' (which is the default for --recend). Each block is passed to sort
       and the output from sort is saved into files. These files are passed to
       the second parallel that runs sort -m on the files before it removes
       the files. The output is saved to bigfile.sort.

Note that it covers two cases, the second being where the process cannot do simple appending.

Best wishes ... cheers, drl
 

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LEARN ABOUT CENTOS

rmf

RMF(1)								     [nmh-1.5]								    RMF(1)

NAME

       rmf - remove an nmh folder

SYNOPSIS

       rmf [+folder] [-interactive | -nointeractive] [-version] [-help]

DESCRIPTION

       Rmf removes all of the messages (files) within the specified (or default) folder, and then removes the folder (directory) itself.

       If  there  are  any  files  within the folder which are not a part of nmh, they will not be removed, and an error will be produced.  If the
       folder is given explicitly or the -nointeractive option is given, then the folder will be removed  without  confirmation.   Otherwise,  the
       user  will be asked for confirmation.  If rmf can't find the current folder, for some reason, the folder to be removed defaults to `+inbox'
       (unless overridden by user's profile entry "Inbox") with confirmation.

       If the folder being removed is a subfolder, the parent folder will become the new current folder, and rmf will produce  a  message  telling
       the user this has happened.  This provides an easy mechanism for selecting a set of messages, operating on the list, then removing the list
       and returning to the current folder from which the list was extracted.

       If rmf s used on a read-only folder, it will delete all the (private) sequences (i.e., "atr-seq-folder" entries) for this folder from  your
       context without affecting the folder itself.

       Rmf irreversibly deletes messages that don't have other links, so use it with caution.

FILES

       $HOME/.mh_profile	  The user profile

PROFILE COMPONENTS

       Path:		    To determine the user's nmh directory
       Current-Folder:	    To find the default current folder
       Inbox:		    To find the default inbox

SEE ALSO

       rmm(1)

DEFAULTS

       `+folder' defaults to the current folder, usually with confirmation
       `-interactive' if +folder' not given, `-nointeractive' otherwise

CONTEXT

       Rmf  will  set the current folder to the parent folder if a subfolder is removed; or if the current folder is removed, it will make "inbox"
       current.  Otherwise, it doesn't change the current folder or message.

BUGS

       Although intuitively one would suspect that rmf works recursively, it does not.	Hence if you have a sub-folder within a folder,  in  order
       to rmf the parent, you must first rmf each of the children.

MH.6.8								   11 June 2012 							    RMF(1)
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