Quick Navigator

Search Site

Unix VPS
A - Starter
B - Basic
C - Preferred
D - Commercial
MPS - Dedicated
Previous VPSs
* Sign Up! *

Contact Us
Online Help
Domain Status
Man Pages

Virtual Servers

Topology Map

Server Agreement
Year 2038

USA Flag



Man Pages
Env(3) Perl Programmers Reference Guide Env(3)

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

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

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;

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

Chip Salzenberg < chip@fin.uucp> and Gregor N. Purdy <>
2018-03-01 perl v5.28.1

Search for    or go to Top of page |  Section 3 |  Main Index

Powered by GSP Visit the GSP FreeBSD Man Page Interface.
Output converted with ManDoc.