MirOS Manual: Env(3p)


Env(3p)         Perl Programmers Reference Guide          Env(3p)

NAME

     Env - perl module that imports environment variables as
     scalars or arrays

SYNOPSIS

         use Env;
         use Env qw(PATH HOME TERM);
         use Env qw($SHELL @LD_LIBRARY_PATH);

DESCRIPTION

     Perl maintains environment variables in a special hash named
     %ENV.  For when this access method is inconvenient, the Perl
     module "Env" allows environment variables to be treated as
     scalar or array variables.

     The "Env::import()" function ties environment variables with
     suitable names to global Perl variables with the same names.
     By default it ties all existing environment variables ("keys
     %ENV") to scalars.  If the "import" function receives argu-
     ments, it takes them to be a list of variables to tie; it's
     okay if they don't yet exist. The scalar type prefix '$' is
     inferred for any element of this list not prefixed by '$' or
     '@'. Arrays are implemented in terms of "split" and "join",
     using $Config::Config{path_sep} as the delimiter.

     After an environment variable is tied, merely use it like a
     normal variable. You may access its value

         @path = split(/:/, $PATH);
         print join("\n", @LD_LIBRARY_PATH), "\n";

     or modify it

         $PATH .= ":.";
         push @LD_LIBRARY_PATH, $dir;

     however you'd like. Bear in mind, however, that each access
     to a tied array variable requires splitting the environment
     variable's string anew.

     The code:

         use Env qw(@PATH);
         push @PATH, '.';

     is equivalent to:

         use Env qw(PATH);
         $PATH .= ":.";

     except that if $ENV{PATH} started out empty, the second
     approach leaves it with the (odd) value "":."", but the

perl v5.8.8                2005-02-05                           1

Env(3p)         Perl Programmers Reference Guide          Env(3p)

     first approach leaves it with ""."".

     To remove a tied environment variable from the environment,
     assign it the undefined value

         undef $PATH;
         undef @LD_LIBRARY_PATH;

LIMITATIONS

     On VMS systems, arrays tied to environment variables are
     read-only. Attempting to change anything will cause a warn-
     ing.

AUTHOR

     Chip Salzenberg <chip@fin.uucp> and Gregor N. Purdy
     <gregor@focusresearch.com>

perl v5.8.8                2005-02-05                           2

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