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Full Discussion: Help with retaining variable scope
Top Forums Shell Programming and Scripting Help with retaining variable scope Post 302555935 by bakunin on Friday 16th of September 2011 06:52:34 AM
Old 09-16-2011
Quote:
Originally Posted by justchill
Can anyone please tell me y the value is not retained.
I respectfully disagree with radoulov. The reason, why your value is not retained is because it is incremented in a subshell. This is not because of the shebang line being ignored or not, but because any command - and "sh" is a command too - is invoking its own process.

You will notice that inside your process the value is retained all right. Consider the following example script:

Code:
#!/bin/ksh

typeset -i iValue=0
typeset   chFile=""

print - "Value before: $iValue"

cat filelist | while read chFile ; do
     (( value += 1 ))
done

print - "Value after: $iValue"

exit 0

But you didn't try to retain the variable throughout a script but you inherited the variable from your commandline environment, modified it in your script and expected it to change it in the orginal commandline environment.

The problem is that when an environment inherits values it does not get the originals but copies of them - with the same names and values but still copies. If you modifiy them you are still modifying the copies, not the originals.

You can overcome this by using the ".", which tells the shell not to start a subshell but execute the script in the environment it already has:

Code:
# sh /some/script.sh
# . sh /some/script.sh

I hope this helps.

bakunin
 

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LEARN ABOUT MOJAVE

cpanplus::shell

CPANPLUS::Shell(3pm)					 Perl Programmers Reference Guide				      CPANPLUS::Shell(3pm)

NAME

       CPANPLUS::Shell - base class for CPANPLUS shells

SYNOPSIS

	   use CPANPLUS::Shell; 	    # load the shell indicated by your
					    # config -- defaults to
					    # CPANPLUS::Shell::Default

	   use CPANPLUS::Shell qw[Classic]  # load CPANPLUS::Shell::Classic;

	   my $ui      = CPANPLUS::Shell->new();
	   my $name    = $ui->which;	    # Find out what shell you loaded

	   $ui->shell;			    # run the ui shell

DESCRIPTION

       This module is the generic loading (and base class) for all "CPANPLUS" shells. Through this module you can load any installed "CPANPLUS"
       shell.

       Just about all the functionality is provided by the shell that you have loaded, and not by this class (which merely functions as a generic
       loading class), so please consult the documentation of your shell of choice.

BUG REPORTS

       Please report bugs or other issues to <bug-cpanplus@rt.cpan.org<gt>.

AUTHOR

       This module by Jos Boumans <kane@cpan.org>.

COPYRIGHT

       The CPAN++ interface (of which this module is a part of) is copyright (c) 2001 - 2007, Jos Boumans <kane@cpan.org>. All rights reserved.

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

SEE ALSO

       CPANPLUS::Shell::Default, CPANPLUS::Shell::Classic, cpanp

perl v5.18.2							    2014-01-06						      CPANPLUS::Shell(3pm)
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