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Env::Bash
Perl extension for accessing _all_ bash environment variables.

Env::Bash - Perl extension for accessing _all_ bash environment variables.



NAME

Env::Bash - Perl extension for accessing _all_ bash environment variables.


SYNOPSIS


  use Env::Bash;

Standard interface:


  my @var = get_env_var( "SORCERER_MIRRORS",

                         Source => "/etc/sorcery/config", );

  print "SORCERER_MIRRORS via get_env_var:\n",

  join( "\n", @var ), "\ncount = ", scalar @var, "\n";

  

  @var = Env::Bash::SORCERER_MIRRORS

      ( Source => "/etc/sorcery/config", );

  print "SORCERER_MIRRORS via name:\n",

  join( "\n", @var ), "\ncount = ", scalar @var, "\n";

  

  my @keys = get_env_keys( Source => "/etc/sorcery/config",

                           SourceOnly => 1, );

  print "first 10 keys:\n", map { " $_\n" } @keys[0..9];

Object oriented interface:


  my $be = Env::Bash->new( Source => "/etc/sorcery/config",

                           Keys => 1, );

  my @var = $be->get( "SORCERER_MIRRORS" );

  print "SORCERER_MIRRORS via get:\n",

  join( "\n", @var ), "\ncount = ", scalar @var, "\n";

      

  @var = $be->SORCERER_MIRRORS;

  print "SORCERER_MIRRORS via name:\n",

  join( "\n", @var ), "\ncount = ", scalar @var, "\n";

  

  $be = Env::Bash->new( Keys => 1,);

  @var = $be->HOSTTYPE;

  print "HOSTTYPE via name:\n",

  join( "\n", @var ), "\ncount = ", scalar @var, "\n";

  

  if( $be->exists( 'BASH_VERSINFO' ) ) {

      print "BASH_VERSINFO =>\n ",

      join( "\n ", $be->BASH_VERSINFO ), "\n";

  }

  

  my %options = $be->options( [], Keys => 1 );

Tie HASH interface:


  my %env = ();

  tie %env, "Env::Bash", Source => "/etc/sorcery/config", ForceArray => 1;

  

  my $var = $env{SORCERER_MIRRORS};

  print "SORCERER_MIRRORS via tied hash:\n",

  join( "\n", @$var ), "\ncount = ", scalar @$var, "\n";

  

  $var = $env{HOSTTYPE};

  print "HOSTTYPE via tied hash:\n",

  join( "\n", @$var ), "\ncount = ", scalar @$var, "\n";

  

  while( my( $key, $value ) = each %env ) {

      print "$key =>\n ", join( "\n ", @$value ), "\n";

  }


DESCRIPTION

Env::Bash enables perl access to ALL bash environment variables ( including those that may be bash arrays ). But you say: ``That doesn't make sense; perl already has the %ENV hash. Why not use that?''. Well, please run:


  $ perl -e 'print "$_ = $ENV{$_}\n" for sort keys %ENV;'

and:


  $ set | grep "^[A-Z]"

Now compare the outputs. See, perl's list is much shorter than the bash list. This is because the environment passed to perl contains only variables that have been exported( I think ). There is no pure-perl way to get all the variables in the running shell; also, forget about getting all the elements of variables that are bash arrays!

In the following discussion and examples, I show how I use this module with Linux Sorcerer. For my fellow Sorcererites, this is fine, for others, please see A SHAMELESS PLUG FOR LINUX SORCERER below.

NOTE: on systems without bash, this module turns into an expensive implementation of $ENV{...}.

Options

The following options, specified as func( ..., key1 => value1, ..., ) are provided.

Debug
Prints debugging information to STDERR.

Values 0 or 1, default 0.

ForceArray or []
Defines how environment variable data are returned. Especially useful if you expect to handle bash array variables. For example, an array variable, 'BASH_VERSINFO', returns data as follows:

                       scalar context      list context

                       --------------      ------------

  ForceArray => 0            3             ( 3,

                                             00,

                                             0,

                                             1.

                                             'release',

                                             'i686-pc-linux-gnu' )

  ForceArray => 1         reference        ( 3,

                          to array           00,

                          returned in        0,

                          list context.      1.

                                             'release',

                                             'i686-pc-linux-gnu' )

As a shortcut, ForceArray may be specified by placing the empty array reference token '[]' as the first, and only first, argument of the option arguments.

Values 0 or 1, default 0.

SelectRegex
The regular expression to select which environment variables to read. It may be any valid perl regular expression.

Values valid perl regex, default: none.

Keys
Whether or not to load an array of environment variable names.

Values 0 or 1, default 0.

Source
The path name of one or more executable bash scripts with which to 'source' ( execute with a leading dot ) before extracting environment. Any variables set in these scripts is then available for this module. The leading dot is prepended if not supplied.

More than one source file may be specified as a scalar of semicolon separated source file names:


  Source => '/etc/bebe/configure.sh;/etc/sorcery/config',

or an array reference:


  Source => [ qw( /etc/bebe/configure.sh /etc/sorcery/config ) ],

Values: any list of executable bash scripts, Default none.

SourceOnly
Returns only the environment variables defined by the Source script(s). Some bash-generated environment variables may 'sneak' through, notably, 'PIPESTATUS'.

Values 0 or 1, default 0.

WARNING
SourceOnly is handled by reading all the current environment variables ( without sourcing the entries in Source ), then reading all the variable ( including Source ), and removing any variable that does not appear in both lists. If you have exported a variable that you are sourcing in the shell where your script will run, it will NOT appear in the returned list. SourceOnly is of limited value and should only be used when you really want only the keys from your sourced scripts. 'get', 'get_env_var', and tie access to variables are not affected by SourceOnly.

Standard interface

The non-object oriented interface.

get_env_var

prototype
get_env_var( options...);

options used
Debug, ForceArray, SelectRegex, Source, SourceOnly.

operation
Returns the contents of the specified environment variable in scalar or list context as described above. If the requested variable is not present, a false value ( not 'undef' ) is returned.

Env::Bash::VARIABLE_NAME

prototype
Env::Bash::VARIABLE_NAME( options...);

note
This is the AUTOLOAD version of 'get_env_var'.

get_env_keys

prototype
get_env_keys( options...);

options used
Debug, ForceArray, SelectRegex, Source, SourceOnly.

operation
Returns a sorted array ( list context ) or an array reference ( scalar context ) of the keys in the current bash environment.

Object oriented interface

new

prototype
Env::Bash->new( options... );

options used
Debug, ForceArray, SelectRegex, Keys, Source, SourceOnly.

operation
Returns a Env::Bash object with the specified options saved in the object so they do not have to be repeated in subsequent method calls.

get

prototype
$env_bash_obj->get( options... );

options used
Debug, ForceArray, SelectRegex, Source, SourceOnly.

operation
Returns the contents of the specified environment variable in scalar or list context as described above. If the requested variable is not present, a false value ( not 'undef' ) is returned.

VARIABLE_NAME

prototype
$env_bash_obj->VARIABLE_NAME( options... );

options used
Debug, ForceArray, SelectRegex, Source, SourceOnly.

operation
This is the AUTOLOAD version of 'get'.

exists

prototype
$env_bash_obj->exists( 'VARIABLE_NAME' );

options used
None.

operation
Returns true or false to indicate whether or not the environment exists.

keys

prototype
$env_bash_obj->keys( options... );

options used
Debug, ForceArray, SelectRegex, Source, SourceOnly.

operation
Returns a sorted array ( list context ) or an array reference ( scalar context ) of the keys in the current bash environment.

reload_keys

prototype
$env_bash_obj->reload_keys( options... );

options used
Debug, ForceArray, SelectRegex, Source, SourceOnly.

operation
Reloads the environment key array and returns a sorted array ( list context ) or an array reference ( scalar context ) of the keys in the current bash environment.

options

prototype
$env_bash_obj->options( options... );

options used
ANY.

operation
Returns a the current options hash after setting any options specified.

Tie HASH interface

tie

prototype

  my %env = ();

  tie %env, "Env::Bash", options...;
options used
Debug, ForceArray, SelectRegex, Keys, Source, SourceOnly.

operation
Ties a hash variable to Env::Bash. The resulting hash may be used like a normal hash, except it is read-only. Note: if ForceArray is specified, the resulting hash is a hash of array references.

hash operations

allowed
access ( $var = $env{SOME_VARIABLE_NAME} ), exists, each, keys, values,

not allowed
assign ( $env{SOME_VARIABLE_NAME} = $var ), delete, clear ( as %env = (); ).

note
Unlike normal hashes, the keys are maintained in sorted order, therefore there is no need tor use the '... sort keys ...' construct unless you wish to process in some non-standard order.

Export

get_env_var and get_env_keys are unconditionally exported.


A SHAMELESS PLUG FOR LINUX SORCERER

Linux Sorcerer, by Kyle Sallee, is a great Linux distribution. It gives you one of the most up-to-date and fastest Linux systems available. Sorcerer is based upon package 'source', not pre-compiled rpm's. You ( with the bash scripts supplied by Sorcerer ) compile and install the packages optimized to your machine. You configure your own kernel for the best, leanest kernel matching your environment. Current packages are made available as soon as they are stable; you do not have to wait six months for the next release of your distribution.

With the gain there is always the pain:

Installing updated packages is slower.
The documentation is wanting.
No fancy 'x' windows installer; the command line rules!
Not for the beginner.

All and all, I love it! Check it out at http://sorcerer.wox.org


BUGS

December 23, 2004
Minor bug in AUTOLOAD in version 0.01. Resolved in 0.02.

December 24, 2004
On systems without a bash executable, revert to using $ENV{...} and skip tests using source scripts ( as on MSWin32 ). Resolved in 0.03.

December 24 2004
Again, on systems without a bash executable, some tests fail. In addition, those systems are bombarded with error messages '...bash not found...'. Resolved in 0.04.


SEE ALSO

The 'Advanced Bash-Scripting Guide' at http://www.tldp.org/LDP/abs/html/.


AUTHOR

Beau E. Cox, <beaucox@hawaii.rr.com>.


COPYRIGHT AND LICENSE

Copyright (C) 2004 by Beau E. Cox.

This library is free software; you can redistribute it and/or modify it under the same terms as Perl itself, either Perl version 5.8.6 or, at your option, any later version of Perl 5 you may have available.

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