


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 inconve-
       nient, 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 vari-
       ables ("keys %ENV") to scalars.  If the "import" function
       receives arguments, it takes them to be a list of vari-
       ables 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::Con-
       fig{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



2000-04-06                 perl v5.6.1                          1





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


       first approach leaves it with ""."".

       To remove a tied environment variable from the environ-
       ment, 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
       warning.

AUTHOR
       Chip Salzenberg <chip@fin.uucp> and Gregor N. Purdy <gre-
       gor@focusresearch.com>








































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