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

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

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

NNAAMMEE #

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

SSYYNNOOPPSSIISS #

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

DDEESSCCRRIIPPTTIIOONN #

 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 .= ":/any/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, '/any/path';

 is almost equivalent to:

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

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

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

     undef $PATH;
     undef @LD_LIBRARY_PATH;

LLIIMMIITTAATTIIOONNSS #

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

AAUUTTHHOORR #

 Chip Salzenberg <_c_h_i_p_@_f_i_n_._u_u_c_p> and Gregor N. Purdy
 <_g_r_e_g_o_r_@_f_o_c_u_s_r_e_s_e_a_r_c_h_._c_o_m>

perl v5.36.3 2023-02-15 Env(3p)