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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 SUNOS
asadmin-export
asadmin-export(1AS) User Commands asadmin-export(1AS) NAME
asadmin-export, export - marks a variable name for automatic export to the environment of subsequent commands in multimode SYNOPSIS
export [ name=value [ name=value]*] Marks a variable name for automatic export to the environment of subsequent commands. All subsequent commands use the variable name values as specified; unless you unset them or exit multimode. If only the variable name is specified, the current value of that variable name is displayed. If the export command is used without any arguments, a list of all the exported variables and their values is displayed. Exported shell environment variables set prior to invoking the asadmin utility are imported automatically and set as exported variables within asadmin. Unexported environment variables cannot be read by the asadmin utility. OPERANDS
name=value variable name and value for automatic export to the environment to be used by subsequent commands. Example 1: Using export to list the environment variables asadmin> export AS_ADMIN_HOST=bluestar AS_ADMIN_PORT=8000 AS_ADMIN_USER=admin AS_ADMIN_PASSWORD=password asadmin> export AS_ADMIN_PREFIX=server1.jms-service asadmin> export //to list the environment variables that are set AS_ADMIN_HOST=bluestar AS_ADMIN_PORT=8000 AS_ADMIN_USER=admin AS_ADMIN_PASSWORD=******** AS_ADMIN_PREFIX=server1.jms-service Where: the export command lists the environment variables that are set. In this case, the environment variables have been set to: the host is bluestar, the port is 8000, the administrator user is admin with an associated password, and the prefix is server1.jms-service. EXIT STATUS
0 command executed successfully 1 error in executing the command asadmin-unset(1AS), asadmin-multimode(1AS) J2EE 1.4 SDK March 2004 asadmin-export(1AS)