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Env

Perl 5 version 8.9 documentation
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Env

NAME

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

SYNOPSIS

  1. use Env;
  2. use Env qw(PATH HOME TERM);
  3. 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

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

or modify it

  1. $PATH .= ":.";
  2. 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:

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

is equivalent to:

  1. use Env qw(PATH);
  2. $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

  1. undef $PATH;
  2. 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>