environment variable

1 definition found

environment variable - Free On-line Dictionary of Computing (26 May 2007) :

  environment variable
  environment
  
     <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.
  
     (1999-01-26)