Index for Section 3

Alphabetical listing for E

Bottom of page

Env(3)
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>

Index for Section 3

Alphabetical listing for E

Top of page