|
|
Sponsored Content
Top Forums
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
|
|
10 More Discussions You Might Find Interesting
1. UNIX for Dummies Questions & Answers
Hello,
I need some help to understand system and user environment files, such as .profile and others. I can edit my .profile file in my home directory. What I only touch in this file is the $PATH variable and when I am logged in under a telnet session, the PATH that I specify is used and... (8 Replies)
Discussion started by: jacobsa
8 Replies
2. UNIX for Dummies Questions & Answers
$ . oraenv (when i type this at the prompt)
ORACLE_SID = ? ( I get this)
I understand that . oraenv is a startup script and it has the ENV variable ORACLE_SID.
But pls let me know what more it explains and also how to change the env variable here. (2 Replies)
Discussion started by: thumsup9
2 Replies
3. Shell Programming and Scripting
First of all I am using C shell.
I have a variable destDirectory that holds a path.
the path includes an environment variable($user)
when I try to execute a command within the script, the $destDirectory gets replaced with the path, but the environment variable is not replaced. I end up... (2 Replies)
Discussion started by: karyn1617
2 Replies
4. Shell Programming and Scripting
i am using the below script and trying to move files in that directory in that pattern to archive. But it doesn;t seem to take the metacharacters. Please sugggest.
Code
Debug output: (1 Reply)
Discussion started by: dsravan
1 Replies
5. Shell Programming and Scripting
Hi,
I have to set bunch of variables and all other programs like make,
perl will use them ..
Here are my constraints and requirements ...
The variables have to be set by executing a script that runs
in c shell. I cannot source the script since people who use this
script might be on... (8 Replies)
Discussion started by: sharanbr
8 Replies
6. Shell Programming and Scripting
Hi all,
I have a variable say var1 (output from somewhere, which I can't change)which store something like this:
echo $var1
name=fred
age=25
address="123 abc"
password=pass1234
how can I make the variable $name, $age, $address and $password contain the info?
I mean do this in a... (1 Reply)
Discussion started by: freddy1228
1 Replies
7. UNIX for Dummies Questions & Answers
Hi!
Ok, so I'm no programmer and I have basically no experience in these stuff. However I need to work on a thing (I think you call it Framework) called Root. It's a tool used by physicists. In the manual they keep talking about Environment variable. Even thou I searched for what it is on the... (5 Replies)
Discussion started by: tirwit
5 Replies
8. Shell Programming and Scripting
I'm trying to make a sed substitution where the substitution pattern is an environment variable to be expanded, but the variable contains a "slash".
sed -e 's/<HOME_DIRECTORY>/'$HOME'/'This gives me the following error:
sed: -e expression #1, char 21: unknown option to `s'Obviously this is... (2 Replies)
Discussion started by: Ilja
2 Replies
9. UNIX for Advanced & Expert Users
Hi all,
I'm bit new to the advanced bash shell scripting.
When I'm looking at some of the existing code in my organization, got confused with a few variable definings.
For ex:
var1={1:-30}
var2="abc def ghi"
var3={xyz:-$var2}
In above, 1st and last lines are confusing me.... (4 Replies)
Discussion started by: raghu.iv85
4 Replies
10. UNIX for Beginners Questions & Answers
Hello,
I am running ubuntu16.04.
By means of @Rudic's help, I have below command.
What I need to do is to replace video_id by value of video_id in which WHERE clause is matched:
{print "INSERT INTO video_series_files (id, video_id, file_type, protocol, \
url, languages, quality, accessed... (12 Replies)
Discussion started by: baris35
12 Replies
LEARN ABOUT DEBIAN
mdbfontencoding
mdbFontEncoding(5) The m17n Library mdbFontEncoding(5) NAME
mdbFontEncoding - Font Encoding DESCRIPTION
The m17n library loads information about the encoding of each font form the m17n database by the tags <font, encoding>. The data is loaded as a plist of this format. FONT-ENCODING ::= PER-FONT * PER-FONT ::= '(' FONT-SPEC ENCODING [ REPERTORY ] ')' FONT-SPEC ::= '(' [ FOUNDRY FAMILY [ WEIGHT [ STYLE [ STRETCH [ ADSTYLE ]]]]] REGISTRY ')' ENCODING ::= SYMBOL FONT-SPEC is to specify properties of a font. FOUNDRY to REGISTRY are symbols corresponding to Mfoundry to Mregistry property of a font. See m17nFont for the meaning of each property. For instance, this FONT-SPEC: (nil alice0 lao iso8859-1) should be applied to all fonts whose family name is 'alice0 lao', and registry is 'iso8859-1'. ENCODING is a symbol representing a charset. A font matching FONT-SPEC supports all characters of the charset, and a character code is mapped to the corresponding glyph code of the font by this charset. REPERTORY is a symbol representing a charset or 'nil'. Omitting it is the same as specifying ENCODING as REPERTORY. If it is not 'nil', the charset specifies the repertory of the font, i.e, which character it supports. Otherwise, whether a specific character is supported by the font or not is asked to each font driver. For so called Unicode fonts (registry is 'iso10646-1'), it is recommended to specify 'nil' as REPERTORY because such fonts usually supports only a subset of Unicode characters. COPYRIGHT
Copyright (C) 2001 Information-technology Promotion Agency (IPA) Copyright (C) 2001-2011 National Institute of Advanced Industrial Science and Technology (AIST) Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License <http://www.gnu.org/licenses/fdl.html>. Version 1.6.2 12 Jan 2011 mdbFontEncoding(5)