Browse Definitions :
Definition

environment variable

Contributor(s): Amittai Aviram

An environment variable defines some aspect of a user's or a program's environment that can vary. Generally set during the login procedure, for a user the environment variable establishes some component of the user's working environment, such as the default printer , browser , or text editor to be used. Because these are preset as values specific to the identified user, they save time that would be used selecting them at each login. Environment variables are used across multiple languages and operating systems to provide information to applications that may be specific to the user request.

The UNIX shell uses environment variables to send information about the user's environment (such as the current working directory or the terminal type, for example) to the programs being run. The variable definitions are passed on to any program that is not built into the shell, and can be consulted, or modified by the program. For example, "TERM" (environment variables are expressed as upper case by programming convention) defines the type of terminal used, "PATH" defines the directories to be searched for programs corresponding to command names, and "USER" defines the particular user, so that access permissions may be checked for each request.

The common gateway interface ( CGI ) uses environment variables that are set when the server executes the gateway program, to pass information about requests from the server to the script . The server sends out environment variable definitions such as "SERVER_SOFTWARE," which identifies the name and version of the responding server software; "SERVER_NAME," which identifies the server's hostname, DNS alias , or Internet Protocol ( IP ) address; and "GATEWAY_INTERFACE," which identifies the CGI specification used. These environment variables are not request-specific, and are sent with every request. Other environment variables are specific to the type of request being sent, such as "SERVER_PROTOCOL," which identifies the name and revision of the protocol used for the request, and "REQUEST_METHOD," which identifies the method used for the request.

This was last updated in September 2005

Continue Reading About environment variable

Join the conversation

1 comment

Send me notifications when other members comment.

Please create a username to comment.

You are doing a great work...Keep it up !!

:)
Cancel

-ADS BY GOOGLE

File Extensions and File Formats

Powered by:

SearchCompliance

SearchSecurity

  • GPS jamming

    GPS jamming is the process of using a frequency transmitting device to block or interfere with radio communications.

  • time-based one-time password (TOTP)

    A time-based one-time password (TOTP) is a temporary code, generated by an algorithm, for use in authenticating access to ...

  • Security Operations Center (SOC)

    A security operations center (SOC) is a command center facility for a team of IT professionals with expertise in information ...

SearchHealthIT

SearchDisasterRecovery

  • disaster recovery team

    A disaster recovery team is a group of individuals focused on planning, implementing, maintaining, auditing and testing an ...

  • cloud insurance

    Cloud insurance is any type of financial or data protection obtained by a cloud service provider. 

  • business continuity software

    Business continuity software is an application or suite designed to make business continuity planning/business continuity ...

SearchStorage

  • SSD (solid-state drive)

    An SSD (solid-state drive) is a type of nonvolatile storage media that stores persistent data on solid-state flash memory.

  • NAND flash memory

    NAND flash memory is a type of nonvolatile storage technology that does not require power to retain data.

  • storage class memory (SCM)

    Storage class memory (SCM) is a type of NAND flash that includes a power source to ensure that data won't be lost due to a system...

Close