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Full Discussion: Speeding up shell script with grep
Top Forums Shell Programming and Scripting Speeding up shell script with grep Post 302994604 by bakunin on Saturday 25th of March 2017 05:27:04 AM
Old 03-25-2017
Quote:
Originally Posted by dunryc
master is a file which has been collated over a few years ad currently contains around 4 million numbers

new is a file which also contains 4 million number i need to split new nto two separate files one which contains number that already exist in master and one which contains numbers that don't already exist in master. I can do this but it takes around 80 hours to complete !! can any one offer any suggestions on how to speed this up ?
Use grep -f: instead of writing a shell loop grep can do it in one step (and presumably quite faster):

Code:
grep -f new_phone master > in_new_phone_and_master

You might want to try this with some small files to get a feeling for what it produces. You can also use all the other grep-options in conjunction withh this, especially "-F" (use fixed strings for matching), which speeds greps operation up considerably. Also notice the -v-option which inverts the outcome. See the man-page of grep for details.

I hope this helps.

bakunin
This User Gave Thanks to bakunin For This Post:
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LEARN ABOUT DEBIAN

vm

VM(1)								      mgetty								     VM(1)

NAME

       vm - VoiceModem is the program for handling the voice modem functionality from shell scripts

ACTIONS

       beep options [<frequency [<length in 0.001sec>]]>
       diagnostics options device name (e.g. ttyS2
       dial options phone number
       help
       play options [<file names]+>
       record options file name
       shell options [<shell script [shell options]]>
       wait  options [<time in seconds]>
       devicetest

OPTIONS

       -c n use compression type n
       -d n set i/o device
       -t, -m, -i, -e, -s, -H equals to -d <2,3,4,5,6,7>
       -l s set device string (e.g. -l ttyS2:ttyC0)
       -v verbose output
       -w use off / on hook signal from local handset to start and stop recording
       -x n set debug level
       -L n set maximum recording length in sec
       -P print first DTMF tone on stdout and exit
       -R read and print DTMF string on stdout and exit
       -S s set default shell for shell scripts (e.g. -S /bin/sh)
       -T n set silence timeout in 0.1sec
       -V n set silence threshold to <n> (0-100%%)

SEE ALSO

       vgetty(1)

POD ERRORS

       Hey! The above document had some coding errors, which are explained below:

       Around line 30:
	   You forgot a '=back' before '=head1'

       Around line 32:
	   '=item' outside of any '=over'

       Around line 71:
	   You forgot a '=back' before '=head1'

perl v5.10.1							    2010-04-04								     VM(1)
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