Provided by: elektra-bin_0.8.14-5.1ubuntu2_amd64 
NAME
kdb-elektrify-getenv - elektrify the environment of applications
SYNOPSIS
kdb elektrify-getenv application options
DESCRIPTION
When an application is elektrified using libelektragetenv, it does not only request
environ, but also Elektra for every getenv(3) and secure_getenv(3) library call.
Its main purpose is to:
• have standard ways to modify the environment
• make relogin (or even restart!) of applications unnecessary
• allow a hierarchical structure for environment
• allow settings to only apply for individual applications or only in special context
• still preserve the advantages (inheriting of environment to subprocesses)
• Availability in at, cron and similar scripts.
It is implemented using a LD_PRELOAD technique, see USAGE below for global activation.
LOOKUPS
The main purpose of this approach is to finally have a well-defined way to set and get
environment variables. Elektra´s variables will be in use immediately for every newly
started application (no relogin necessary).
To do so, getenv(3) will lookup multiple sources next to searching in the environment
(environ). As running example will use getenv("HOME") -> /path/to/home:
1. Given commandline parameters will always be preferred (see OPTIONS below).
E.g. kdb elektrify-getenv <app> --elektra:HOME=/path/to/home
2. Then /env/override/<key> will be looked up, where key is the parameter to getenv. If
found, the key will be returned, if it is a null keys, getenv will return NULL.
E.g. kdb set user/env/override/HOME /path/to/home
3. Then environment will be requested.
E.g. HOME=/path/to/home kdb elektrify-getenv <application>
4. Then /env/fallback/<key> will be looked up. If found, the key will be returned, if it
is a null keys, getenv will return NULL.
E.g. kdb set user/env/fallback/HOME /path/to/home
OPTIONS
When elektrify-getenv is active, every application additionally accepts Elektra´s getenv
options. Interleaving Elektra´s and the application´s options is allowed. Elektra will
parse its options (starting with --elektra) first and discard them before the other
application is started. Therefore the application will not see that they even existed,
e.g.: given kdb elektrify-getenv <application> -V --elektra-debug -L the application will
be called with <application> -V -L.
Internal Options
--elektra-help
Outputs this help.
--elektra-version
Gives version information.
--elektra-debug=file, ELEKTRA_DEBUG or /env/option/debug
Trace all getenv(3) calls to a file. stderr if no file is given, e.g. kdb set
user/env/option/debug "". Note that null values (no forth argument), will disable
debug messages. See examples below.
--elektra-clearenv, ELEKTRA_CLEARENV or /env/option/clearenv
Call clearenv(3) before entering main. This is a recommended security feature.
Elektra itself, if configured that way, will still be able to use the environment.
--elektra-reload-timeout=time_in_ms, ELEKTRA_RELOAD_TIMEOUT or /env/option/reload_timeout
Activate a timeout based feature when a time is given in ms (and is not 0).
Internal Options are available in three different variants:
1. as commandline parameter: --elektra-<option>, which are not passed through exec(3)
calls.
2. as environment variable: ELEKTRA_<OPTION>. which might be passed through exec(3)
calls, but are removed by clearenv(3) calls.
3. as Elektra KDB entry: /env/option/<option>, which are the way to achieve an option to
be enabled for every application.
E.g. kdb set user/env/option/clearenv "" to clear the environment for all applications
started by that user (note that at least PATH should to be set using kdb set
user/env/fallback/PATH "/bin:/usr/bin" then).
Note, that null keys are equal to non-set options. E.g. kdb set
system/env/option/debug "/tmp/elektra.log" and kdb set user/env/option/debug will
activate logging for the system, except for the current user.
Contextual Options
--elektra%<name>%=<value> or /env/layer/<name>
Add the contextual information (=layer) %<name>% with it´s value <value>. Note that
%name% is predefined with argv[0] and %basename% with basename(argv[0]).
Values can contain / to form hierarchies, e.g. --elektra%name%=app/profile
Options for Applications
--elektra:key=value, /env/override/<key> or /env/fallback/<key>
set a key/value to be preferred, i.e. the first to considered as explained in
LOOKUP.
Keys can contain / to form hierarchies, e.g. --elektra:my/HOME=/path/to/home.
USAGE
To always use Elektra´s getenv environment, simply add the output to the file:
kdb elektrify-getenv | tail -1 | sudo tee -a /etc/ld.so.preload
this also can be done using Elektra:
sudo kdb mount /etc/ld.so.preload system/ld/preload line null
sudo kdb set "system/ld/preload/new" `kdb elektrify-getenv | tail -1`
CONTEXT
The metadata context in the specification can be used to facilitate a context-dependent
lookup. In its metavalue all replacements of %<name>% will be replaced by the given
contextual options --elektra%<name>%=<value> and /env/layer/<name> keys.
E.g. to have a different home directory for any user and application:
kdb set user/env/layer/user markus
kdb set user/users/markus/konqueror/HOME /home/download
kdb setmeta spec/env/override/HOME context /users/%user%/%name%/HOME
BUGS
Some applications do not use getenv(3) or secure_getenv(3) for requesting the environment,
e.g. shells. This approach cannot work for them.
In the startup-phase (before main is even entered), getenv(3) will not consider
/env/override/ or /env/fallback.
Elektra internally tries to avoid using the environment. Some resolvers, however, use it
to be conform to some specifications, e.g. XDG. Depending on the setup you use, these
parameters might be used. For more information see:
kdb info resolver
For these parameters, /env/override/ or /env/fallback will not be used internally, but
will be used if applications request them, too.
If you use the standard resolvers, the bug won´t have any effect.
Also note that --elektra-debug or ELEKTRA_DEBUG does not log getenv(3) used by plugins
during the startup-phase.
Commandline Arguments are always to the outmost command, e.g. nice ls --elektra:COLUMNS=20
won´t have any effect because only for nice COLUMNS will be set.
EXAMPLES
For illustration this section gives some more examples.
kdb elektrify-getenv man man --elektra:MANWIDTH=40
Will use MANWIDTH 40 for this invocation of man man. This feature is handy, if an option
is only available by environment, but not by command-line arguments, because sometimes
environment variables are not trivial to set (e.g. in Makefiles).
Debugging:
# system wide to stderr (not recommended!):
sudo kdb set system/env/option/debug ""
# system wide to /var/log/elektra.log:
sudo kdb set system/env/option/debug "/var/log/error.log"
# but for my user to ~/.elektra.log:
kdb set user/env/option/debug "$HOME/.elektra.log"
# or disable it for my user:
kdb set user/env/option/debug
Some more examples:
kdb set user/env/override/MANOPT -- "--regex -LC"
kdb elektrify-getenv getenv MANOPT # to check if it is set as expected
kdb getenv MANOPT # if /etc/ld.so.preload is active
Will permanently and user-wide change MANOPT to include --regex, and -LC so that regular
expressions will be used (note man echo will return many man pages then) and that they
will be shown in English. This feature is handy to change the default behaviour of
applications (either system, user or directory-wide).
kdb set system/env/override/HTTP_PROXY http://proxy.hogege.com:8000/
Will permanently and system-wide change the proxy for all applications that honor
HTTP_PROXY, e.g. w3m. We can also link http_proxy to the value of HTTP_PROXY:
kdb setmeta spec/env/override/http_proxy "override/#0" /env/override/HTTP_PROXY
kdb get /env/override/http_proxy
July 2017 KDB-ELEKTRIFY-GETENV(1)