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Full Discussion: Using xargs for multiple functions
Top Forums Shell Programming and Scripting Using xargs for multiple functions Post 302436181 by methyl on Friday 9th of July 2010 12:35:10 PM
Old 07-09-2010
Quote:
for i in `nawk '/From/ {print $3}' syslogs | uniq`; do grep $i syslogs >> $i
More points:
1) This is not a good command structure for an open ended list because it leaves the shell with a potentially massive "for" command to process.
We can turn the "for" into a "while" and remove that issue.
2) We need to "sort" the node selection or "uniq" will not work properly and we will be making selections multiple times.
3) We can replace ">>" with ">" because each file is now only written once.
4) The "cat" to a pipeline was harmless and can be quicker at getting records into "awk" than getting "awk" to read the file direct. I've left it out because it is the convention of this board.

Overall this should be quicker and more importantly should not give multiple repeat blocks of data because of the missing "sort".

Code:
nawk '/From/ {print $3}' syslogs | sort | uniq | while read node
do
      grep "${node}" syslogs > "${node}"
done

Last edited by methyl; 07-09-2010 at 01:36 PM.. Reason: typos
This User Gave Thanks to methyl For This Post:
krypton
 

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LEARN ABOUT LINUX

uniq

UNIQ(1) 							   User Commands							   UNIQ(1)

NAME

       uniq - report or omit repeated lines

SYNOPSIS

       uniq [OPTION]... [INPUT [OUTPUT]]

DESCRIPTION

       Filter adjacent matching lines from INPUT (or standard input), writing to OUTPUT (or standard output).

       With no options, matching lines are merged to the first occurrence.

       Mandatory arguments to long options are mandatory for short options too.

       -c, --count
	      prefix lines by the number of occurrences

       -d, --repeated
	      only print duplicate lines

       -D, --all-repeated[=delimit-method]
	      print all duplicate lines delimit-method={none(default),prepend,separate} Delimiting is done with blank lines

       -f, --skip-fields=N
	      avoid comparing the first N fields

       -i, --ignore-case
	      ignore differences in case when comparing

       -s, --skip-chars=N
	      avoid comparing the first N characters

       -u, --unique
	      only print unique lines

       -z, --zero-terminated
	      end lines with 0 byte, not newline

       -w, --check-chars=N
	      compare no more than N characters in lines

       --help display this help and exit

       --version
	      output version information and exit

       A field is a run of blanks (usually spaces and/or TABs), then non-blank characters.  Fields are skipped before chars.

       Note:  'uniq'  does  not  detect  repeated  lines unless they are adjacent.  You may want to sort the input first, or use `sort -u' without
       `uniq'.	Also, comparisons honor the rules specified by `LC_COLLATE'.

AUTHOR

       Written by Richard M. Stallman and David MacKenzie.

REPORTING BUGS

       Report uniq bugs to bug-coreutils@gnu.org
       GNU coreutils home page: <http://www.gnu.org/software/coreutils/>
       General help using GNU software: <http://www.gnu.org/gethelp/>
       Report uniq translation bugs to <http://translationproject.org/team/>

COPYRIGHT

       Copyright (C) 2010 Free Software Foundation, Inc.  License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>.
       This is free software: you are free to change and redistribute it.  There is NO WARRANTY, to the extent permitted by law.

SEE ALSO

       comm(1), join(1)

       The full documentation for uniq is maintained as a Texinfo manual.  If the info and uniq programs are properly installed at your site,  the
       command

	      info coreutils 'uniq invocation'

       should give you access to the complete manual.

GNU coreutils 8.5						   February 2011							   UNIQ(1)
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