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Full Discussion: Explanation of FNR in this awk script
Top Forums Shell Programming and Scripting Explanation of FNR in this awk script Post 302944633 by yifangt on Wednesday 20th of May 2015 06:46:05 PM
Old 05-20-2015
Explanation of FNR in this awk script
To merge mutiple *.tab files as:
file1.tab
Code:
rs1 A A
rs2 A A
rs3 C C
rs4 C C

file2.ind
Code:
rs1 T T
rs2 T T
rs3 G G
rs4 G G

and file3.tab
Code:
rs1 B B
rs2 B B
rs3 L L
rs4 L L

Output：
Code:
file1.tab  file2.tab  file3.tab
AA       TT       BB
AA       TT       BB
CC       GG       LL
CC       GG       LL

which could be done with:
Code:
awk 'BEGIN{for(i=1;i<ARGC;i++)printf ARGV[i]" ";print ""}{a[FNR]=length(a[FNR])?a[FNR]$2$3FS:$2$3FS}END{for(i=0;i++<FNR;)print a[i]}' *.tab

I have hard time to understand a[FNR] and a[FNR]=length(a[FNR]) in the part:
Code:
a[FNR]=length(a[FNR])?a[FNR]$2$3FS:$2$3FS

Can anybody please explain it for me?
Thanks a lot!
Last edited by yifangt; 05-20-2015 at 08:00 PM..
 

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LEARN ABOUT MOJAVE

locale::codes::langvar

Locale::Codes::LangVar(3pm)				 Perl Programmers Reference Guide			       Locale::Codes::LangVar(3pm)

NAME

       Locale::Codes::LangVar - standard codes for language variation identification

SYNOPSIS

	  use Locale::Codes::LangVar;

	  $lvar = code2langvar('acm');		       # $lvar gets 'Mesopotamian Arabic'
	  $code = langvar2code('Mesopotamian Arabic'); # $code gets 'acm'

	  @codes   = all_langvar_codes();
	  @names   = all_langvar_names();

DESCRIPTION

       The "Locale::Codes::LangVar" module provides access to standard codes used for identifying language variations, such as those as defined in
       the IANA language registry.

       Most of the routines take an optional additional argument which specifies the code set to use. If not specified, the default IANA language
       registry codes will be used.

SUPPORTED CODE SETS

       There are several different code sets you can use for identifying language variations. A code set may be specified using either a name, or
       a constant that is automatically exported by this module.

       For example, the two are equivalent:

	  $lvar = code2langvar('en','alpha-2');
	  $lvar = code2langvar('en',LOCALE_CODE_ALPHA_2);

       The codesets currently supported are:

       alpha
	   This is the set of alphanumeric codes from the IANA language registry, such as 'arevela' for Eastern Armenian.

	   This code set is identified with the symbol "LOCALE_LANGVAR_ALPHA".

	   This is the default code set.

ROUTINES

       code2langvar ( CODE [,CODESET] )
       langvar2code ( NAME [,CODESET] )
       langvar_code2code ( CODE ,CODESET ,CODESET2 )
       all_langvar_codes ( [CODESET] )
       all_langvar_names ( [CODESET] )
       Locale::Codes::LangVar::rename_langvar  ( CODE ,NEW_NAME [,CODESET] )
       Locale::Codes::LangVar::add_langvar  ( CODE ,NAME [,CODESET] )
       Locale::Codes::LangVar::delete_langvar  ( CODE [,CODESET] )
       Locale::Codes::LangVar::add_langvar_alias  ( NAME ,NEW_NAME )
       Locale::Codes::LangVar::delete_langvar_alias  ( NAME )
       Locale::Codes::LangVar::rename_langvar_code  ( CODE ,NEW_CODE [,CODESET] )
       Locale::Codes::LangVar::add_langvar_code_alias  ( CODE ,NEW_CODE [,CODESET] )
       Locale::Codes::LangVar::delete_langvar_code_alias  ( CODE [,CODESET] )
	   These routines are all documented in the Locale::Codes::API man page.

SEE ALSO

       Locale::Codes
	   The Locale-Codes distribution.

       Locale::Codes::API
	   The list of functions supported by this module.

       http://www.iana.org/assignments/language-subtag-registry
	   The IANA language subtag registry.

AUTHOR

       See Locale::Codes for full author history.

       Currently maintained by Sullivan Beck (sbeck@cpan.org).

COPYRIGHT

	  Copyright (c) 2011-2013 Sullivan Beck

       This module is free software; you can redistribute it and/or modify it under the same terms as Perl itself.

perl v5.18.2							    2014-01-06					       Locale::Codes::LangVar(3pm)
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