NAME
Env::C - Get/Set/Unset Environment Variables on the C level
VERSION
version 0.15
SYNOPSIS
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");DESCRIPTION
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 setenv_multi and 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.
FUNCTIONS
getenv($key)
Returns the value of the environment variable matching the key or undef.
setenv($key, $value, [$override])
The setenv() function adds the variable $key to the environment with the value $value, if $key does not already exist. If $key does exist in the environment, then its value is changed to $value if $override is non-zero; if $override is zero or is not passed, then the value of $key is not changed.
unsetenv($key)
The unsetenv() function deletes the variable $key from the environment.
setenv_multi($key1, $value1, $override1, $key2, $value2, $override2, ...)
Similar to setenv, but works with several variables at once.
unsetenv_multi(@keys)
Similar to unsetenv, but works with several variables at once.
getallenv()
my $ar_env = Env::C::getallenv();
print join "\n", @$ar_env;The getallenv() function returns an array reference which includes all the environment variables.
EXPORT
None.
Thread-safety and Thread-locality
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).
HISTORY
Versions 0.01 through 0.08 written and maintained by Stas Bekman <stas@stason.org>
SOURCE
The development version is on github at https://github.com/mschout/env-c and may be cloned from git://github.com/mschout/env-c.git
BUGS
Please report any bugs or feature requests to bug-env-c@rt.cpan.org or through the web interface at: http://rt.cpan.org/Public/Dist/Display.html?Name=Env-C
AUTHOR
Michael Schout <mschout@cpan.org>
COPYRIGHT AND LICENSE
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.