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 ?
To estimate the effect of information environment variables on SPS this study uses panel data analysis.
The supplier must provide a leadership model and a related questionnaire that is scientifically substantiated and adequately addressed the diversity of leadership styles and the ability to vary according to the environment variables (contextual levels) that ask for it.
For instance, management of environment variables and parameters often can be automated so that developers don't need to specify them by hand.
The impacts of this change are still being realized more than 3 years after the combat training centers shifted operational environment variables toward a decisive-action training environment to facilitate meeting the brigade combat team commander's new training objectives.
Questions on the uncertain and complex environment variables were prepared exclusively for this research.
Data of whether the IPO listed enterprises' raise funds changed or not came from CCER; listed enterprise financial indicators among corporate governance variables and control variables came from CSMAR; institutional environment variables came from CEInet Industry Database, website of State-owned Assets Supervision and Administration Commission of the State Council, and the Statistical Yearbook of China issued by the National Bureau of Statistics of the People's Republic of China.
This resulted in the technological development of adaptive bitrate--delivery of a lower-quality stream appropriate to bandwidth and other end-user environment variables.
On Windows, you can modify your environment variables by opening the Control Panel > System and Security > System > Advanced system settings > Environment Variables.
Higher scores for all built environment variables reflected increased perceived supportiveness of the neighbourhood environment for walking.
Second, a one-factor ANOVA was performed to discover whether there were significant differences among the three comparison groups on the school environment variables (teacher support, affiliation and involvement) and academic self-concept, and on the family environment variables (family cohesion and family conflict) and family self-concept.
What model will be used depends on the cell type, frequency, area type and other environment variables.
We then conducted the cross-sectional analyses of the associations of the GIS walkable built environment variables with BMI z-score.

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