awk NR==FNR output control Post: 302532027

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Top Forums UNIX for Dummies Questions & Answers awk NR==FNR output control Post 302532027 by agama on Sunday 19th of June 2011 11:06:04 AM

06-19-2011

Registered User

The short answer is to process f2 first, then process f1. This will reduce your memory footprint as you'll only save 68 things in a[] rather than 48K things.

The long answer is to be a bit more clever which might also help speed things up. Your programme will loop through the entire contents of file f1 for each record in f2 (48,000 * 68) testing to see if there's a match. Instead, use the hash capabilities of awk to your advantage.

This example assumes that the 'key' (field 1 in file 2) can occur multiple times and so we must do a bit of looping for each f1 record, but the only looping needed when reading limited to the number of duplicate 'keys' that existed in f2 for the current f1 record. If f2 will not have duplicates, then the code can be simplified more, but not knowing you exact data, this general case will work for either. We also don't need to make an explicit check to see if the key in the current record matches the one saved from f2.

Code:

awk -v f2=f2 '
    BEGIN {
        while( (getline<f2) > 0 )   # read and collect records from f2
        {
            key = $1;
            ki = kidx[key]++;        # track number of duplicate keys (0 based)
            k2rec[key,ki] = $0;      # save unique record by key and dup count
        }
        close( f2 );
    }

    {
        key = $3;
        for( i = 0; i < kidx[key]; i++ )          # for each duplicate of key
            printf( "%s\t%s\n", k2rec[key,i], $0 );   # print f2 record, followed by current f1 record
    }
' <f1 >f3

Hope this makes sense.

Last edited by agama; 06-19-2011 at 12:07 PM.. Reason: Corrected printf to output f2 then f1

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tdbtool

TDBTOOL(8)																TDBTOOL(8)

NAME

       tdbtool - manipulate the contents TDB files

SYNOPSIS

       tdbtool

       tdbtool TDBFILE [COMMANDS...]

DESCRIPTION

       This tool is part of the samba(1) suite.

       tdbtool	a  tool  for  displaying and altering the contents of Samba TDB (Trivial DataBase) files. Each of the commands listed below can be
       entered interactively or provided on the command line.

COMMANDS

       create TDBFILE
	  Create a new database named TDBFILE.

       open TDBFILE
	  Open an existing database named TDBFILE.

       erase
	  Erase the current database.

       dump
	  Dump the current database as strings.

       cdump
	  Dump the current database as connection records.

       keys
	  Dump the current database keys as strings.

       hexkeys
	  Dump the current database keys as hex values.

       info
	  Print summary information about the current database.

       insert KEY DATA
	  Insert a record into the current database.

       move KEY TDBFILE
	  Move a record from the current database into TDBFILE.

       store KEY DATA
	  Store (replace) a record in the current database.

       show KEY
	  Show a record by key.

       delete KEY
	  Delete a record by key.

       list
	  Print the current database hash table and free list.

       free
	  Print the current database and free list.

       ! COMMAND
	  Execute the given system command.

       first
	  Print the first record in the current database.

       next
	  Print the next record in the current database.

       quit
	  Exit tdbtool.

CAVEATS

       The contents of the Samba TDB files are private to the implementation and should not be altered with tdbtool.

VERSION

       This man page is correct for version 3.0.25 of the Samba suite.

AUTHOR

       The original Samba software and related utilities were created by Andrew Tridgell. Samba is now developed by the  Samba	Team  as  an  Open
       Source project similar to the way the Linux kernel is developed.

																	TDBTOOL(8)

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