Environment Variable

What Does Environment Variable Mean?

Environment variables are values that impact the processes and behavior of running computer systems and OS environments. Running programs may access environment variable values for configuration purposes.

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Techopedia Explains Environment Variable

For example, a specifically named environment variable may identify the computer OS location used for temporary file storage. The Microsoft Windows environment variable for temporary file storage is %TEMP% or %TMP%.

Unix systems have specific and proprietary environment variables. A new process inherits a duplicate parent environment from its parent without changes to the parent. These conversions must occur at the application programming interface (API) level between fork and exec. In contrast, environment variables for specific command executions alter shell platforms – such as bash – by invoking env.

Although all UNIX and Microsoft OSs have environment variables, names are never shared by OS programmers. For design purposes, running programs can manipulate environment variable values. Unix callers determine memory spaces running with various setuid program authorities. The dynamic linker loads corresponding code, known as environment variable locations (LD_LIBRARY_PATH and LD_PRELOAD). Code runs according to the process authority.

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Margaret Rouse
Technology Expert

Margaret is an award-winning technical writer and teacher known for her ability to explain complex technical subjects to a non-technical business audience. Over the past twenty years, her IT definitions have been published by Que in an encyclopedia of technology terms and cited in articles by the New York Times, Time Magazine, USA Today, ZDNet, PC Magazine, and Discovery Magazine. She joined Techopedia in 2011. Margaret's idea of a fun day is helping IT and business professionals learn to speak each other’s highly specialized languages.