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.