Environments

An environment is created every time a shell is initialized an environment is just a map of key-value pairs

• Each command is executed in its own environment, which includes (but not limited to):
  1. files that have been sourced
  2. current working directory
  3. functions defined during execution, or inherited from shell's parent in the environment
• When a non-builtin command is executed, it is invoked in a separate execution environment.

Environment Variables

Since every instance of a shell is a separate process, we have a different set of environment variables in each shell

• they can be seen by running env
  • That isn’t all the variables that are set in your shell, though. It’s just the environment variables that are exported to processes that you start in the shell.
• compgen -v allows us to see all variables available in shell
• export allows us to add parameters and functions to the environment
• When a non-builtin command is executed, it is invoked in a separate execution environment.

Export

• Exported variables get passed on to child processes, not-exported variables do not.
  • When we use export in bash, we are adding the variable onto the shell's list of all env variables. This list is exclusive to the shell. When this shell creates a child process, all of these env variables are made available to it.
  • This means that if we only need the variable in the current environment, then we don't need to use export

the environment variables that an application can see are based on how the application was launched (from the dock, from the commandline, etc)

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Backlinks

• Process