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| 3.1.1 Shell Operation
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| The following is a brief description of the shell’s operation when it reads and executes a command. Basically, the shell does the following:
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| # Reads its input from a file (see [[#Shell Scripts|Shell Scripts]]), from a string supplied as an argument to the -c invocation option (see [[#Invoking Bash|Invoking Bash]]), or from the user’s terminal.
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| # Breaks the input into words and operators, obeying the quoting rules described in [[#Quoting|Quoting]]. These tokens are separated by metacharacters. Alias expansion is performed by this step (see [[#Aliases|Aliases]]).
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| # Parses the tokens into simple and compound commands (see [[#Shell Commands|Shell Commands]]).
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| # Performs the various shell expansions (see Shell Expansions), breaking the expanded tokens into lists of filenames (see Filename Expansion) and commands and arguments.
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| # Performs any necessary redirections (see Redirections) and removes the redirection operators and their operands from the argument list.
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| # Executes the command (see Executing Commands).
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| # Optionally waits for the command to complete and collects its exit status (see Exit Status).
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