08-16-2015
Hi, for Posix compliant shells:
- There are shell variables and environment variables
- When a shell starts it makes a copy of the environment variables and creates shell variables with the same name and value, with the export attribute set (marked for export)
- If new shell variables are created in a shell, then they are not marked for export
- The export command sets the export attribute of the shell variables (marks them for export).
- A subprocess inherits all shell variables marked for export (and also variable assignments that are part of the command)
- A subshell is a special kind of subprocess that inherits all shell variables, even those not marked for export.
- The env command (since it is executed as a subprocess) shows the environment variables that would be inherited by a subprocess.
subshells are created implicitly by the shell syntax or explicitly using parentheses
( .... )
Last edited by Scrutinizer; 08-16-2015 at 04:04 PM..
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LEARN ABOUT DEBIAN
envstore
ENVSTORE(1) BSD General Commands Manual ENVSTORE(1)
NAME
envstore -- save and restore environment variables
SYNOPSIS
envstore command [args ...]
DESCRIPTION
envstore can save and restore environment variables, thus transferring them between different shells.
command must be one of
clear
Forget all stored variables
eval
Produce shell code for evaluation, restoring all saved variables
list
List saved variables in better readable format
save variable [value]
Save variable either with its current shell value or with value
rm variable
Remove variable from store
Note: Only the first character of command is checked, so envstore e instead of envstore eval, envstore c for envstore clear, etc., are also
valid.
ENVIRONMENT
ENVSTORE_FILE The file in which the environment parameters are stored, /tmp/envstore-EUID by default,
LIMITATIONS
Variable names or values must not contain null bytes or newlines.
Due to limitations imposed by most shells, it is not possible to save parameters containing more than one consecutive whitespace. envstore
will save and display them correctly, but unless you do IFS trickery, your shell will not be able to load them.
The current maximum length (in bytes) is 255 bytes for the variable name and 1023 bytes for its content.
AUTHOR
envstore was written by Daniel Friesel <derf@derf.homelinux.org>.
Original idea and script by Maximilian Gass <mxey@ghosthacking.net>.
SEE ALSO
envify(1)
BSD
December 1, 2009 BSD