perl/lib/Env.pm

package Env;

our $VERSION = '1.00';

=head1 NAME

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

=head1 SYNOPSIS

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

=head1 DESCRIPTION

Perl maintains environment variables in a special hash named C<%ENV>.  For
when this access method is inconvenient, the Perl module C<Env> allows
environment variables to be treated as scalar or array variables.

The C<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 (C<keys %ENV>) to scalars.  If
the C<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 C<split> and C<join>, using
C<$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 C<$ENV{PATH}> started out empty, the second approach leaves
it with the (odd) value "C<:.>", but the first approach leaves it with "C<.>".

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

    undef $PATH;
    undef @LD_LIBRARY_PATH;

=head1 LIMITATIONS

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

=head1 AUTHOR

Chip Salzenberg E<lt>F<chip@fin.uucp>E<gt>
and
Gregor N. Purdy E<lt>F<gregor@focusresearch.com>E<gt>

=cut

sub import {
    my ($callpack) = caller(0);
    my $pack = shift;
    my @vars = grep /^[\$\@]?[A-Za-z_]\w*$/, (@_ ? @_ : keys(%ENV));
    return unless @vars;

    @vars = map { m/^[\$\@]/ ? $_ : '$'.$_ } @vars;

    eval "package $callpack; use vars qw(" . join(' ', @vars) . ")";
    die $@ if $@;
    foreach (@vars) {
        my ($type, $name) = m/^([\$\@])(.*)$/;
        if ($type eq '$') {
            tie ${"${callpack}::$name"}, Env, $name;
        } else {
            if ($^O eq 'VMS') {
                tie @{"${callpack}::$name"}, Env::Array::VMS, $name;
            } else {
                tie @{"${callpack}::$name"}, Env::Array, $name;
            }
        }
    }
}

sub TIESCALAR {
    bless \($_[1]);
}

sub FETCH {
    my ($self) = @_;
    $ENV{$$self};
}

sub STORE {
    my ($self, $value) = @_;
    if (defined($value)) {
        $ENV{$$self} = $value;
    } else {
        delete $ENV{$$self};
    }
}

######################################################################

package Env::Array;
 
use Config;
use Tie::Array;

@ISA = qw(Tie::Array);

my $sep = $Config::Config{path_sep};

sub TIEARRAY {
    bless \($_[1]);
}

sub FETCHSIZE {
    my ($self) = @_;
    my @temp = split($sep, $ENV{$$self});
    return scalar(@temp);
}

sub STORESIZE {
    my ($self, $size) = @_;
    my @temp = split($sep, $ENV{$$self});
    $#temp = $size - 1;
    $ENV{$$self} = join($sep, @temp);
}

sub CLEAR {
    my ($self) = @_;
    $ENV{$$self} = '';
}

sub FETCH {
    my ($self, $index) = @_;
    return (split($sep, $ENV{$$self}))[$index];
}

sub STORE {
    my ($self, $index, $value) = @_;
    my @temp = split($sep, $ENV{$$self});
    $temp[$index] = $value;
    $ENV{$$self} = join($sep, @temp);
    return $value;
}

sub PUSH {
    my $self = shift;
    my @temp = split($sep, $ENV{$$self});
    push @temp, @_;
    $ENV{$$self} = join($sep, @temp);
    return scalar(@temp);
}

sub POP {
    my ($self) = @_;
    my @temp = split($sep, $ENV{$$self});
    my $result = pop @temp;
    $ENV{$$self} = join($sep, @temp);
    return $result;
}

sub UNSHIFT {
    my $self = shift;
    my @temp = split($sep, $ENV{$$self});
    my $result = unshift @temp, @_;
    $ENV{$$self} = join($sep, @temp);
    return $result;
}

sub SHIFT {
    my ($self) = @_;
    my @temp = split($sep, $ENV{$$self});
    my $result = shift @temp;
    $ENV{$$self} = join($sep, @temp);
    return $result;
}

sub SPLICE {
    my $self = shift;
    my $offset = shift;
    my $length = shift;
    my @temp = split($sep, $ENV{$$self});
    if (wantarray) {
        my @result = splice @temp, $self, $offset, $length, @_;
        $ENV{$$self} = join($sep, @temp);
        return @result;
    } else {
        my $result = scalar splice @temp, $offset, $length, @_;
        $ENV{$$self} = join($sep, @temp);
        return $result;
    }
}

######################################################################

package Env::Array::VMS;
use Tie::Array;

@ISA = qw(Tie::Array);
 
sub TIEARRAY {
    bless \($_[1]);
}

sub FETCHSIZE {
    my ($self) = @_;
    my $i = 0;
    while ($i < 127 and defined $ENV{$$self . ';' . $i}) { $i++; };
    return $i;
}

sub FETCH {
    my ($self, $index) = @_;
    return $ENV{$$self . ';' . $index};
}

1;
Revision:	1.1
Committed:	Thu Jun 30 14:27:08 2005 UTC (21 years, 3 months ago) by root
Branch:	MAIN
CVS Tags:	PERL-5-8-7, HEAD
Branch point for:	PERL
Log Message:	* empty log message *
#	User	Rev	Content
1	root	1.1	package Env;
2
3			our $VERSION = '1.00';
4
5			=head1 NAME
6
7			Env - perl module that imports environment variables as scalars or arrays
8
9			=head1 SYNOPSIS
10
11			use Env;
12			use Env qw(PATH HOME TERM);
13			use Env qw($SHELL @LD_LIBRARY_PATH);
14
15			=head1 DESCRIPTION
16
17			Perl maintains environment variables in a special hash named C<%ENV>. For
18			when this access method is inconvenient, the Perl module C<Env> allows
19			environment variables to be treated as scalar or array variables.
20
21			The C<Env::import()> function ties environment variables with suitable
22			names to global Perl variables with the same names. By default it
23			ties all existing environment variables (C<keys %ENV>) to scalars. If
24			the C<import> function receives arguments, it takes them to be a list of
25			variables to tie; it's okay if they don't yet exist. The scalar type
26			prefix '$' is inferred for any element of this list not prefixed by '$'
27			or '@'. Arrays are implemented in terms of C<split> and C<join>, using
28			C<$Config::Config{path_sep}> as the delimiter.
29
30			After an environment variable is tied, merely use it like a normal variable.
31			You may access its value
32
33			@path = split(/:/, $PATH);
34			print join("\n", @LD_LIBRARY_PATH), "\n";
35
36			or modify it
37
38			$PATH .= ":.";
39			push @LD_LIBRARY_PATH, $dir;
40
41			however you'd like. Bear in mind, however, that each access to a tied array
42			variable requires splitting the environment variable's string anew.
43
44			The code:
45
46			use Env qw(@PATH);
47			push @PATH, '.';
48
49			is equivalent to:
50
51			use Env qw(PATH);
52			$PATH .= ":.";
53
54			except that if C<$ENV{PATH}> started out empty, the second approach leaves
55			it with the (odd) value "C<:.>", but the first approach leaves it with "C<.>".
56
57			To remove a tied environment variable from
58			the environment, assign it the undefined value
59
60			undef $PATH;
61			undef @LD_LIBRARY_PATH;
62
63			=head1 LIMITATIONS
64
65			On VMS systems, arrays tied to environment variables are read-only. Attempting
66			to change anything will cause a warning.
67
68			=head1 AUTHOR
69
70			Chip Salzenberg E<lt>F<chip@fin.uucp>E<gt>
71			and
72			Gregor N. Purdy E<lt>F<gregor@focusresearch.com>E<gt>
73
74			=cut
75
76			sub import {
77			my ($callpack) = caller(0);
78			my $pack = shift;
79			my @vars = grep /^[\$\@]?[A-Za-z_]\w*$/, (@_ ? @_ : keys(%ENV));
80			return unless @vars;
81
82			@vars = map { m/^[\$\@]/ ? $_ : '$'.$_ } @vars;
83
84			eval "package $callpack; use vars qw(" . join(' ', @vars) . ")";
85			die $@ if $@;
86			foreach (@vars) {
87			my ($type, $name) = m/^([\$\@])(.*)$/;
88			if ($type eq '$') {
89			tie ${"${callpack}::$name"}, Env, $name;
90			} else {
91			if ($^O eq 'VMS') {
92			tie @{"${callpack}::$name"}, Env::Array::VMS, $name;
93			} else {
94			tie @{"${callpack}::$name"}, Env::Array, $name;
95			}
96			}
97			}
98			}
99
100			sub TIESCALAR {
101			bless \($_[1]);
102			}
103
104			sub FETCH {
105			my ($self) = @_;
106			$ENV{$$self};
107			}
108
109			sub STORE {
110			my ($self, $value) = @_;
111			if (defined($value)) {
112			$ENV{$$self} = $value;
113			} else {
114			delete $ENV{$$self};
115			}
116			}
117
118			######################################################################
119
120			package Env::Array;
121
122			use Config;
123			use Tie::Array;
124
125			@ISA = qw(Tie::Array);
126
127			my $sep = $Config::Config{path_sep};
128
129			sub TIEARRAY {
130			bless \($_[1]);
131			}
132
133			sub FETCHSIZE {
134			my ($self) = @_;
135			my @temp = split($sep, $ENV{$$self});
136			return scalar(@temp);
137			}
138
139			sub STORESIZE {
140			my ($self, $size) = @_;
141			my @temp = split($sep, $ENV{$$self});
142			$#temp = $size - 1;
143			$ENV{$$self} = join($sep, @temp);
144			}
145
146			sub CLEAR {
147			my ($self) = @_;
148			$ENV{$$self} = '';
149			}
150
151			sub FETCH {
152			my ($self, $index) = @_;
153			return (split($sep, $ENV{$$self}))[$index];
154			}
155
156			sub STORE {
157			my ($self, $index, $value) = @_;
158			my @temp = split($sep, $ENV{$$self});
159			$temp[$index] = $value;
160			$ENV{$$self} = join($sep, @temp);
161			return $value;
162			}
163
164			sub PUSH {
165			my $self = shift;
166			my @temp = split($sep, $ENV{$$self});
167			push @temp, @_;
168			$ENV{$$self} = join($sep, @temp);
169			return scalar(@temp);
170			}
171
172			sub POP {
173			my ($self) = @_;
174			my @temp = split($sep, $ENV{$$self});
175			my $result = pop @temp;
176			$ENV{$$self} = join($sep, @temp);
177			return $result;
178			}
179
180			sub UNSHIFT {
181			my $self = shift;
182			my @temp = split($sep, $ENV{$$self});
183			my $result = unshift @temp, @_;
184			$ENV{$$self} = join($sep, @temp);
185			return $result;
186			}
187
188			sub SHIFT {
189			my ($self) = @_;
190			my @temp = split($sep, $ENV{$$self});
191			my $result = shift @temp;
192			$ENV{$$self} = join($sep, @temp);
193			return $result;
194			}
195
196			sub SPLICE {
197			my $self = shift;
198			my $offset = shift;
199			my $length = shift;
200			my @temp = split($sep, $ENV{$$self});
201			if (wantarray) {
202			my @result = splice @temp, $self, $offset, $length, @_;
203			$ENV{$$self} = join($sep, @temp);
204			return @result;
205			} else {
206			my $result = scalar splice @temp, $offset, $length, @_;
207			$ENV{$$self} = join($sep, @temp);
208			return $result;
209			}
210			}
211
212			######################################################################
213
214			package Env::Array::VMS;
215			use Tie::Array;
216
217			@ISA = qw(Tie::Array);
218
219			sub TIEARRAY {
220			bless \($_[1]);
221			}
222
223			sub FETCHSIZE {
224			my ($self) = @_;
225			my $i = 0;
226			while ($i < 127 and defined $ENV{$$self . ';' . $i}) { $i++; };
227			return $i;
228			}
229
230			sub FETCH {
231			my ($self, $index) = @_;
232			return $ENV{$$self . ';' . $index};
233			}
234
235			1;