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Full Discussion: Help with retaining variable scope
Top Forums Shell Programming and Scripting Help with retaining variable scope Post 302555938 by radoulov on Friday 16th of September 2011 06:58:25 AM
Old 09-16-2011
Quote:
Originally Posted by bakunin
I respectfully disagree with radoulov. The reason, why your value is not retained is because it is incremented in a subshell.
Hi bakunin,
if I'm not missing something, in the OP's example the value of the variable is not incremented in a subshell
(unless executed by the Bourne shell, because it seems that sh uses a subshell for redirected loops):

Code:
while read ...
Value=`expr $Value + $Count`
...
echo "Value=$Value"

Something like:

Code:
$ unset v
$ while read ; do v=$REPLY; done<<<1
$ echo $v
1

The OP is verifying the value of the variable inside the script, not outside of it.

Your cat ... | while read ... example demonstrates another KornShell feature: the last builtin command in a pipeline being executed in the parent shell.

Consider the following examples:

Code:
$ echo ok > infile
$ sh -c 'cat infile | while read v; do myvar=$v;done; echo $myvar'

$ bash -c 'cat infile | while read v; do myvar=$v;done; echo $myvar'

$ ksh -c 'cat infile | while read v; do myvar=$v;done; echo $myvar'
ok

This is because of the previously mentioned KornShell feature.

And this is the OP's case:

Code:
$ echo ok > infile
$ sh -c 'while read v; do myvar=$v;done<infile; echo $myvar'

$ ksh -c 'while read v; do myvar=$v;done<infile; echo $myvar'
ok
$ bash -c 'while read v; do myvar=$v;done<infile; echo $myvar'
ok

In this case the old Bourne shell behaves differently.

Regards
radoulov

P.S. Actually this aspect of some implementations of the Bourne shell is covered in the FAQ.
Last edited by radoulov; 09-16-2011 at 09:33 AM.. Reason: Clarification.
 

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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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