Shell study note

Posted 2020-08-13 bob

5.1

printenv	view Global variables
bash	new shell
set	Global variables and local variables
export test	Local → Global, so it can be accessed in both subshell and main shell.
unset test	Delete a variable, no $ needed.
PATH=$PATH:...	append PATH, no “” needed, export needed to make it global.
.bashrc	define own aliases

User-defined variables are lower-cased; while sys variables are upper.

test=testing;

remember there is no BLANK;

bash: new a shell, the subshell has no $test variable for it is user-defined; so it is with the subshell.

To fix this, we can “export test”, and NO $ needed.

When unset a global var, it only influent the subshell who execute this cmd.