Handbook:Parts/Working/EnvVar/es

Introducción
Una variable de entorno es un objeto designado para contener información usada por una o más aplicaciones. Algunos usuarios (especialmente aquellos nuevos en Linux) encuentran esto un poco extraño o inmanejable. Sin embargo esto no es cierto: usando variables de entorno hace que cualquiera pueda cambiar una opción de configuración para una o más aplicaciones fácilmente.

Ejemplos Importantes
La siguiente tabla muestra un listado de variables de entorno usado por un sistema Linux y describe su uso. Valores de ejemplo se muestran después de la tabla.

A continuación puedes encontrar ejemplos de definiciones para todas estas variables:

El directorio /etc/env.d
To centralize the definitions of these variables, Gentoo introduced the directory. Inside this directory a number of files are available, such as, , etc. which contain the variables needed by the application mentioned in their name.

For instance, when is installed, a file called  was created by the ebuild which contains the definitions of the following variables:

Other distributions might tell their users to change or add such environment variable definitions in or other locations. Gentoo on the other hand makes it easy for the user (and for Portage) to maintain and manage the environment variables without having to pay attention to the numerous files that can contain environment variables.

For instance, when is updated, the  file is updated too without requesting any user-interaction.

This not only benefits Portage, but also the user. Occasionally users might be asked to set a certain environment variable system-wide. As an example we take the http_proxy variable. Instead of messing about with, users can now just create a file (say ) and enter the definition(s) in it:

Usando el mismo fichero para todas las variables, se obtiene una visión rápida de las variables que hay definidas para uno mismo.

El guión env-update
Several files in define the PATH variable. This is not a mistake: when is executed, it will append the several definitions before it updates the environment variables, thereby making it easy for packages (or users) to add their own environment variable settings without interfering with the already existing values.

The script will append the values in the alphabetical order of the  files. The file names must begin with two decimal digits.

The concatenation of variables does not always happen, only with the following variables: ADA_INCLUDE_PATH, ADA_OBJECTS_PATH , CLASSPATH , KDEDIRS , PATH , LDPATH , MANPATH , INFODIR , INFOPATH , ROOTPATH , CONFIG_PROTECT , CONFIG_PROTECT_MASK , PRELINK_PATH , PRELINK_PATH_MASK , PKG_CONFIG_PATH , and PYTHONPATH. For all other variables the latest defined value (in alphabetical order of the files in ) is used.

It is possible to add more variables into this list of concatenate-variables by adding the variable name to either COLON_SEPARATED or SPACE_SEPARATED variables (also inside an file).

When executing, the script will create all environment variables and place them in (which is used by ). It will also extract the information from the LDPATH variable and use that to create. After this, it will run to recreate the  file used by the dynamical linker.

To notice the effect of immediately after running it, execute the following command to update the environment. Users who have installed Gentoo themselves will probably remember this from the installation instructions:

Específicas de usuario
It might not be necessary to define an environment variable globally. For instance, one might want to add and the current working directory (the directory the user is in) to the PATH variable but do not want all other users on the system to have that in their PATH too. To define an environment variable locally, use or :

After logout/login, the PATH variable will be updated.

Específicas de sesión
En ocasiones, se requieren definiciones aún más estrictas. Puede querer usar binarios de un directorio temporal que ha creado sin tener que usar la trayectoria completa a los binarios o sin editar. Para estos momentos necesitará esto.

In this case, just define the PATH variable in the current session by using the command. As long as the user does not log out, the PATH variable will be using the temporary settings.