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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; |