5.1
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printenv |
view Global variables |
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bash |
new shell |
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set |
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export test |
Local → Global, so it can be accessed in both subshell and main shell. |
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Delete a variable, no $ needed. |
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PATH=$PATH:... |
append PATH, no “” needed, export needed to make it global. |
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.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.
原文：http://www.cnblogs.com/xiaochou/p/Shell_study_note.html