select a record from one file matching from second file using awk - Shell Programming and Scripting

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select a record from one file matching from second file using awk

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#6 (permalink)

06-09-2008

era

Herder of Useless Cats (On Sabbatical)

Join Date: Mar 2008

Location: /there/is/only/bin/sh

Posts: 3,652

Oh, I misunderstood your problem description. Here's something which hopefully is closer to what you wanted.

Code:

awk -F , -v acct=root 'NR==FNR { h[$1]++; next; }
{ if($1 == "") $1=host; host=$1; if (! h[$1]) next;
if ($2 == acct) print }' fileb filea

The NR==FNR condition is true while fileb is being read. This is a common awk idiom for reading in a file of auxiliary data before the main processing. The host names in fileb will be used to populate the array h. Then in the main body of the script, if the first field is empty, the value of the host variable will be used for $1. Then the current value of $1 will be remembered in host in case the next line(s) have empty first fields. Then, if the array h does not contain the current host name (meaning it was not present in fileb), the current line is skipped. Finally, if the second field is identical to the variable acct, the line is printed.

(Really old variants of awk do not support passing in variables with the -v option -- if you have this problem, see if you can find nawk or mawk or gawk on your system, or an XPG4 awk. Or you can interpolate the variable directly into the script.)