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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 302994613 by RudiC on Saturday 25th of March 2017 06:20:42 AM
Old 03-25-2017
Using grep -f works, but with two files as large as indicated will take its (serious) time, and may eventually run out of memory. Try
Code:
sort master.csv new | uniq -d

, then use the resultant file in similar way (uniq -u) to extract unique values from either original file.
Comparison of both approaches on ~20k files:
Code:
time grep -ffile2 file1
real    0m0.352s
user    0m0.280s
sys     0m0.052s
time sort file[12] | uniq -d
real    0m0.037s
user    0m0.032s
sys     0m0.004s

EDIT: Times spent for two files with roughly 4E6 entries each, and about 1E6 lines overlap (on a two processor linux host):
Code:
time sort file[12] | uniq -d > f1
real    0m14.975s
user    0m27.048s
sys     0m0.792s
time sort file1 f1 | uniq -u > f2
real    0m9.331s
user    0m16.488s
sys     0m0.572s

Last edited by RudiC; 03-25-2017 at 01:22 PM..
 

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LEARN ABOUT OSF1

uudemon

uudemon(4)						     Kernel Interfaces Manual							uudemon(4)

NAME

       uudemon.admin,  uudemon.cleanu,	uudemon.hour,  uudemon.poll  -	Administrative shell scripts for polling remote systems, cleaning up spool
       directories, reporting status to the system administrator, and routine invocations of the uuxqt and uusched daemons

SYNOPSIS

       These shell scripts reside in the following directory:
	  /usr/lib/uucp

DESCRIPTION

       All the scripts can be run from the command line or can be run automatically by the cron daemon. To automatically run the  scripts,  remove
       the comment character (#) from the beginning of the relevant line in the /var/spool/cron/crontabs/uucp file.

       This  script  reports  status  to  the system administrator. It issues the uustat command to find out the status of uucp jobs. It mails the
       results to the uucp login ID. The script may be modified to send mail to any login ID such as the uucp administrative login ID  (uucpa)	or
       root.  This script cleans up the /var/spool/uucp and /var/spool/uucppublic directories by running the uucleanup command. The uucleanup com-
       mand is run with the following parameters: -C7, -D7, X2, -o2, -W1.  This script runs the uusched and uuxqt daemons in the background.  This
       script  polls  the  systems  listed  in	the  /usr/lib/uucp/Poll file.  The uudemon.poll script should be scheduled before the uudemon.hour
       script. This allows uudemon.poll to create any command files before cron runs the uudemon.hour script.

FILES

       Contains the uudemon.admin, uudemon.cleanu, uudemon.hour and uudemon.poll files.  Contains the uucp file.

RELATED INFORMATION

       Commands: cron(8), uucleanup(8), uusched(8), uuxqt(1)

       Files: /usr/lib/uucp delim off

																	uudemon(4)
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