bash: Shell Operation
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1 3.1.1 Shell Operation
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1 The following is a brief description of the shell's operation when it
1 reads and executes a command. Basically, the shell does the following:
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1 1. Reads its input from a file (⇒Shell Scripts), from a string
11 supplied as an argument to the '-c' invocation option (⇒
Invoking Bash), or from the user's terminal.
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1 2. Breaks the input into words and operators, obeying the quoting
1 rules described in ⇒Quoting. These tokens are separated by
11 'metacharacters'. Alias expansion is performed by this step (⇒
Aliases).
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11 3. Parses the tokens into simple and compound commands (⇒Shell
Commands).
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1 4. Performs the various shell expansions (⇒Shell Expansions),
11 breaking the expanded tokens into lists of filenames (⇒
Filename Expansion) and commands and arguments.
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1 5. Performs any necessary redirections (⇒Redirections) and
1 removes the redirection operators and their operands from the
1 argument list.
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1 6. Executes the command (⇒Executing Commands).
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1 7. Optionally waits for the command to complete and collects its exit
1 status (⇒Exit Status).
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