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.
This article is provided by FOLDOC - Free Online Dictionary of Computing (foldoc.org)

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.
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References in periodicals archive ?
This assessment instrument measures the fidelity of the implementation of practices associated with the Pyramid Model in center-based infant and toddler classrooms, and it provides a picture of the adult behaviors and classroom environment variables associated with supporting and promoting the social-emotional development of infants and toddlers.
'We know [our] exact emotions but can't give it words,' she said, while explaining the brain activity related to emotions based on different external factors, such as genetic variables, personality references and environment variables.
The main objectives of this study are (a) to identify the frequency of concordance/discordance on home environment factors (e.g., parental encouragement to diet, family functioning) among adolescents, mothers, and fathers; and (b) to examine the relationship between triadic concordance/discordance on home environment variables and adolescent disordered eating behaviors.
The other approach is the assessment of classroom learning environment variables based on students' perceptions about their classrooms.
You can also add the path to the SDK to Windows' environment variables, so you can run the console anywhere.
Our main objective is to develop a new learning algorithm to map occupant's feedback and indoor environment variables into personalized thermal preference profiles while addressing the above-mentioned practical limitations related to the implementation of customized indoor environments in office buildings.
Null hypothesis H0: significant difference does not exist in the distribution of multiproject environment variables among the stakeholder category.
These additional measures would allow further isolating the influence of sleep environment variables.
After controlling sociodemographics and other built environment variables, URT still has a significant impact on car ownership, which echoes other recent studies [10, 11, 16].
To estimate the effect of information environment variables on SPS this study uses panel data analysis.
Model 1 included the objectively measured neighborhood environment variables. Model 2 included comparable perceived neighborhood environment variables.

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