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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 MOJAVE
git-var
GIT-VAR(1) Git Manual GIT-VAR(1) NAME
git-var - Show a Git logical variable SYNOPSIS
git var ( -l | <variable> ) DESCRIPTION
Prints a Git logical variable. OPTIONS
-l Cause the logical variables to be listed. In addition, all the variables of the Git configuration file .git/config are listed as well. (However, the configuration variables listing functionality is deprecated in favor of git config -l.) EXAMPLE
$ git var GIT_AUTHOR_IDENT Eric W. Biederman <ebiederm@lnxi.com> 1121223278 -0600 VARIABLES
GIT_AUTHOR_IDENT The author of a piece of code. GIT_COMMITTER_IDENT The person who put a piece of code into Git. GIT_EDITOR Text editor for use by Git commands. The value is meant to be interpreted by the shell when it is used. Examples: ~/bin/vi, $SOME_ENVIRONMENT_VARIABLE, "C:Program FilesVimgvim.exe" --nofork. The order of preference is the $GIT_EDITOR environment variable, then core.editor configuration, then $VISUAL, then $EDITOR, and then the default chosen at compile time, which is usually vi. GIT_PAGER Text viewer for use by Git commands (e.g., less). The value is meant to be interpreted by the shell. The order of preference is the $GIT_PAGER environment variable, then core.pager configuration, then $PAGER, and then the default chosen at compile time (usually less). SEE ALSO
git-commit-tree(1) git-tag(1) git-config(1) GIT
Part of the git(1) suite Git 2.17.1 10/05/2018 GIT-VAR(1)