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# Using Variables To expand a variable in shell script, prefix the variable name with a dollar sign. For example: \begin{md} ``` foo=hello echo $foo ``` \end{md} The variable \begin{md}`$foo`\end{md} is substituted with its value, if any, after the expansion. In the above example, \begin{md}`$foo`\end{md} expands to `hello`, so the output looks like this: ``` hello ```