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("
", @LD_LIBRARY_PATH), "
";
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 v5.18.2 2013-11-04 Env(3pm)
Check Out this Related Man Page
File::SearchPath(3pm) User Contributed Perl Documentation File::SearchPath(3pm)NAME
File::SearchPath - Search for a file in an environment variable path
SYNOPSIS
use File::SearchPath qw/ searchpath /;
$file = searchpath( 'libperl.a', env => 'LD_LIBRARY_PATH' );
$file = searchpath( 'my.cfg', env => 'CFG_DIR', subdir => 'ME' );
$path = searchpath( $file, env => 'PATH', exe => 1 );
$path = searchpath( $file, env => 'PATH', dir => 1 );
$file = searchpath( 'ls', $ENV{PATH} );
$exe = searchpath( 'ls' );
DESCRIPTION
This module provides the ability to search a path-like environment variable for a file (that does not necessarily have to be an
executable).
FUNCTIONS
The following functions can be exported by this module.
searchpath
This is the core function. The only mandatory argument is the name of a file to be located. The filename should not be absolute
although it can include directory specifications.
$path = searchpath( $file );
@matches = searchpath( $file );
If a second argument is provided, it is assumed to be a path like variable. This interface is provided for backwards compatibility with
"File::SearchPath" version 0.01. It is not as portable as specifying the name of the environment variable. Note also that no specific
attempt will be made to check whether the file is executable when the subroutine is called in this way.
$path = searchpath( $file, $ENV{PATH} );
By default, this will search in $PATH for executable files and is equivalent to:
$path = searchpath( $file, env => 'PATH', exe => 1 );
Hash-like options can be used to alter the behaviour of the search:
env Name of the environment variable to use as a starting point for the search. Should be a path-like environment variable such as
$PATH, $LD_LIBRARY_PATH etc. Defaults to $PATH. An error occurs if the environment variable is not set or not defined. If it is
defined but contains a blank string, the current directory will be assumed.
exe If true, only executable files will be located in the search path. If $PATH is being searched, the default is for this to be
true. For all other environment variables the default is false. If "dir" option is specified "exe" will always default to
false.
dir If true, only directories will be located in the search path. Default is false. "dir" and "exe" are not allowed to be true in
the same call. (triggering a croak() on error).
subdir If you know that your file is in a subdirectory of the path described by the environment variable, this direcotry can be
specified here. Alternatively, the path can be included in the file name itself.
In scalar context the first match is returned. In list context all matches are returned in the order corresponding to the directories
listed in the environment variable.
Returns undef (or empty list) if no match could be found.
If an absolute file name is provided, that filename is returned if it exists and is readable, else undef is returned.
HISTORY
"File::SearchPath" used to exist on CPAN (now on backpan) and was written by Robert Spier. This version is completely new but retains an
interface that is compatible with Robert's version. Thanks to Robert for allowing me to reuse this module name.
NOTES
If "Env::Path" module is installed it will be used. This allows for more flexibility than simply assuming colon-separated paths.
SEE ALSO
Env::Path, File::Which, File::Find, File::Find::Run, File::Where.
AUTHOR
Tim Jenness <t.jenness@jach.hawaii.edu>
Copyright (C) 2005,2006, 2008 Particle Physics and Astronomy Research Council. Copyright (C) 2009-2010 Science and Technology Facilities
Council. All Rights Reserved.
This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or (at your option) any later version.
This program is distributed in the hope that it will be useful,but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
You should have received a copy of the GNU General Public License along with this program; if not, write to the Free Software Foundation,
Inc., 59 Temple Place,Suite 330, Boston, MA 02111-1307, USA
perl v5.14.2 2012-03-28 File::SearchPath(3pm)