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UNIX for Dummies Questions & Answers
Environment variable definition
Post 302952252 by niels on Sunday 16th of August 2015 01:12:25 PM
08-16-2015
Environment variable definition
I'm a bit confused about the term ‘environment variables'.
Within your shell you can set two types of variables:
1. Shell variable - affecting functionality within your shell
2. User defined variable
When using the ‘export' command on a variable you make sure it's being inherited by new sub shells / sub processes.
After using the ‘export' command on a user defined variable it will be showed by the command ‘env' - not before exporting it.
Now the confusing part.
After looking up the definition of ‘environment variables' on multiple sites it is being described as being the ‘shell variables'.
But why is an exported ‘user defined variable' being showed by the ‘env' command?
This is implying that exporting a variable makes it part of the ‘environment' so the definition is based on the inheritance and not the effect on the shell.
But the command ‘env' is already showing the shell variables that are not exported that contradicts the above.
---------- Post updated at 12:12 PM ---------- Previous update was at 11:39 AM ----------
I've found a site that is stating ‘environment variables' are defined as exported variables that are available to sub shells. (at support.sas.com)
This matches the fact that exported ‘user defined' variables are shown by the ‘env' command.
It can be confusing that a lot of books / sites are referring to an environment variables as being a shell variable in general.
Within your shell you can set two types of variables:
1. Shell variable - affecting functionality within your shell
2. User defined variable
When using the ‘export' command on a variable you make sure it's being inherited by new sub shells / sub processes.
After using the ‘export' command on a user defined variable it will be showed by the command ‘env' - not before exporting it.
Now the confusing part.
After looking up the definition of ‘environment variables' on multiple sites it is being described as being the ‘shell variables'.
But why is an exported ‘user defined variable' being showed by the ‘env' command?
This is implying that exporting a variable makes it part of the ‘environment' so the definition is based on the inheritance and not the effect on the shell.
But the command ‘env' is already showing the shell variables that are not exported that contradicts the above.
---------- Post updated at 12:12 PM ---------- Previous update was at 11:39 AM ----------
I've found a site that is stating ‘environment variables' are defined as exported variables that are available to sub shells. (at support.sas.com)
This matches the fact that exported ‘user defined' variables are shown by the ‘env' command.
It can be confusing that a lot of books / sites are referring to an environment variables as being a shell variable in general.
Last edited by Scrutinizer; 08-16-2015 at 01:52 PM.. Reason: Typo
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LEARN ABOUT XFREE86
vconsole.conf
VCONSOLE.CONF(5) vconsole.conf VCONSOLE.CONF(5) NAME
vconsole.conf - configuration file for the virtual console SYNOPSIS
/etc/vconsole.conf DESCRIPTION
The /etc/vconsole.conf file configures the virtual console, i.e. keyboard mapping and console font. The basic file format of the vconsole.conf is a newline-separated list environment-like shell-compatible variable assignments. It is possible to source the configuration from shell scripts, however, beyond mere variable assignments no shell features are supported, allowing applications to read the file without implementing a shell compatible execution engine. Note that the kernel command line options vconsole.keymap=, vconsole.keymap.toggle=, vconsole.font=, vconsole.font.map=, vconsole.font.unimap= may be used to override the console settings at boot. Depending on the operating system other configuration files might be checked for configuration of the virtual console as well, however only as fallback. OPTIONS
The following options are understood: KEYMAP=, KEYMAP_TOGGLE= Configures the key mapping table of for they keyboard. KEYMAP= defaults to us if not set. The KEYMAP_TOGGLE= can be used to configured a second toggle keymap and is by default unset. FONT=, FONT_MAP=, FONT_UNIMAP= Configures the console font, the console map and the unicode font map. FONT= defaults to latarcyrheb-sun16. EXAMPLE
Example 1. German keyboard and console /etc/vconsole.conf: KEYMAP=de-latin1 FONT=latarcyrheb-sun16 SEE ALSO
systemd(1), loadkeys(1), setfont(8), locale.conf(5) AUTHOR
Lennart Poettering <lennart@poettering.net> Developer systemd 10/07/2013 VCONSOLE.CONF(5)