- Thread-safety and Thread-locality
- COPYRIGHT AND LICENSE
Env::C - Get/Set/Unset Environment Variables on the C level
use Env::C; my $key = "USER"; $val = Env::C::getenv($key) || ''; Env::C::setenv($key, "foobar", [$override]); $new_val = Env::C::getenv($key) || ''; Env::C::unsetenv($key); my $ar_env = Env::C::getallenv(); print join "\n", @$ar_env; Env::C::setenv_multi( "VAR1", "value1", 1, "VAR2", "value2", 0 ); Env::C::unsetenv_multi("VAR1", "VAR2");
This module provides a Perl API for getenv(3), setenv(3) and unsetenv(3). It also can return all the
environ variables. You also can use
getenv_multi for bulk operations with environment.
Sometimes Perl invokes modules with underlaying C APIs which rely on certain environment variables to be set. If these variables are set in Perl and the glue code doesn't worry to set them on the C level, these variables might not be seen by the C level. This module shows what really the C level sees.
Returns the value of the environment variable matching the key or
setenv() function adds the variable
$key to the environment with the value
$key does not already exist. If
$key does exist in the environment, then its value is changed to
$override is non-zero; if
$override is zero or is not passed, then the value of
$key is not changed.
The unsetenv() function deletes the variable
$key from the environment.
setenv, but works with several variables at once.
unsetenv, but works with several variables at once.
my $ar_env = Env::C::getallenv(); print join "\n", @$ar_env;
getallenv() function returns an array reference which includes all the environment variables.
This module should not be used in a threaded enviroment.
The OS, which maintains the struct
environ, shares it between all threads in the process, which means it is not thread-local. So if you modify it in one thread, all other threads will see the new value. Something that will most likely break the code.
This module is not thread-safe, since two threads may attempt to modify/read the struct
environ at the same time. I could add locking if in a threaded environment. However since the lock can't be seen by other applications, they can still bypass it causing race condition. But since thread-locality is not maintained, making this module thread-safe is useless.
If you need to modify the C level of
%ENV for all threads to see, do that before threads are started. (e.g. for mod_perl 2.0, at the server startup).
Versions 0.01 through 0.08 written and maintained by Stas Bekman <email@example.com>
Please report any bugs or feature requests to firstname.lastname@example.org or through the web interface at: http://rt.cpan.org/Public/Dist/Display.html?Name=Env-C
Michael Schout <email@example.com>
This software is copyright (c) 2002 by Michael Schout.
This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself.