manpagez: man pages & more
man Env(3)
Home | html | info | man
Env(3pm)               Perl Programmers Reference Guide               Env(3pm)




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 arguments, 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 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 warning.


AUTHOR

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



perl v5.24.0                      2016-02-05                          Env(3pm)

perl 5.24 - Generated Sun Nov 6 18:15:01 CST 2016
© manpagez.com 2000-2017
Individual documents may contain additional copyright information.