environment variable

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environment variable

(programming, operating system)
A variable that is bound in the current environment. When evaluating an expression in some environment, the evaluation of a variable consists of looking up its name in the environment and substituting its value.

Most programming languages have some concept of an environment but in Unix shell scripts it has a specific meaning slightly different from other contexts. In shell scripts, environment variables are one kind of shell variable. They differ from local variables and command line arguments in that they are inheritted by a child process. Examples are the PATH variable that tells the shell the file system paths to search to find command executables and the TZ variable which contains the local time zone. The variable called "SHELL" specifies the type of shell being used.

These variables are used by commands or shell scripts to discover things about the environment they are operating in. Environment variables can be changed or created by the user or a program.

To see a list of environment variables type "setenv" at the csh or tcsh prompt or "set" at the sh, bash, jsh or ksh prompt.

In other programming languages, e.g. functional programming languages, the environment is extended with new bindings when a function's parameters are bound to its actual arguments or when new variables are declared. In a block-structured procedural language, the environment usually consists of a linked list of activation records.

environment variable

An item of memory-resident data that provides a mechanism for users, applications and the operating system to interact with each other. Set up in memory by the operating system each time it is booted, the variables hold the current environment configuration, such as computer and login name, CPU type and the names of the system, application, home and temporary folders.

Command Line Assistance
A common environment variable is the Path, which holds any number of folder hierarchies that the OS can search when a program is run at the command line so that the full path to the executable does not have to be explicitly entered each time. See path environment variable and path.
References in periodicals archive ?
On Windows, you can modify your environment variables by opening the Control Panel > System and Security > System > Advanced system settings > Environment Variables.
We analyzed the impact of one built environment variable on BMI at a time, partly due to collinearity between built environments shown in previous research (Leal et al.
The environment variable, without considering whether it is uncertain or complex, influences the organizational innovation, which means that the service companies take into consideration the behavior of external factors that affect the organization to conduct activities of organizational innovation; this is related to the works of: Damanpour (2010), who states that innovations are influenced by the market conditions (2); and McCrea and Betts (2008), who indicate that innovations allow companies to better respond to changes in the environment.
Enmeshment between the parent and child may also be more likely in families with a depressed parent, although this family environment variable has received less attention.
First, if H1 proves true, then the Collaborative NPD Environment variable is anticipated to have a positive indirect effect on the Supplier Involvement variable via the Manufacturing Involvement variable.
The purpose of this study is to advance our understanding of the urban faculty work environment, and to examine relationships between work environment variables and the job satisfaction, organizational commitment, and turnover intentions of urban university faculty.
The name of the web site making the request can be passed to the program in the QUERY_STRING environment variable.
The responses for each question were added together to correspond with the learning environment variable the question was listed under.
The present study aims to expand population ecology research to include legal changes as another institutional environment variable that may affect organizational founding rates.
By the way, the c:\dos\ (pathname) part of this statement is stored in the COMSPEC environment variable which is how DOS is able to locate the command interpreter when it needs to be relocated from disk.
recognizes an even more comprehensive list of equipment configurations including environment variable and device driver changes.

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