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 ?
The study also assesses key market environment variables, evaluates company market share and profiles 37 global industry players.
We hope to contribute to the existing body of knowledge by answering the following research questions: 'Are these built environment variables closely and consistently correlated to the obesity problem throughout the US?
We then conducted the cross-sectional analyses of the associations of the GIS walkable built environment variables with BMI z-score.
3 processes trailing strings after function definitions in the values of environment variables, which allows remote attackers to execute arbitrary code via a crafted environment , as demonstrated by vectors involving the ForceCommand feature in OpenSSH sshd, the mod_cgi and mod_cgid modules in the Apache HTTP Server, scripts executed by unspecified DHCP clients, and other situations in which setting the environment occurs across a privilege boundary from Bash execution, aka "ShellShock.
Among the topics are developing an English classroom environment inventory and its application in China, the effects of psychosocial learning environment on students' attitudes towards mathematics, developing generic capabilities in teaching and learning environments at the associate degree level, linking teaching and learning environment variables to higher order thinking skills, and investigating factorial invariance of teacher climate factors across school organization levels.
According to the reviewed paper, there is a relation between the environment variables and the organizational innovation, and between each of the different dimensions of such variables; McCrea and Betts (2008) point out that innovations allow companies to get a competitive edge, in addition to becoming more capable of responding to the dynamic environment.
Further, the institutional environment variables are strongly related to corporate governance practices, while culture is less correlated with corporate governance practices.
To sum up, relevant studies on the regional unemployment problem show that the factors that affect Regional unemployment can be categorized into three major sets of variables, namely, regional characteristic variables, macro environment variables and spatial-neighborhood effect variables.
Use and personalize windows environment variables to find data and files.
Panel C reports the interest rate environment variables.
With this objective we propose the hypothesis that dimensional and social status variables of individual trees reflect the effects of stand density, treatments, site index, and other growing environment variables.
Additionally, an included power calculator allows FPGA designers to analyze and optimize power requirements early in the design process block level by the changing of design environment variables.

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