Executing Commands (Bash Reference Manual)

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3.7 Executing Commands

Simple Command Expansion    How Bash expands simple commands before executing them.
Command Search and Execution    How Bash finds commands and runs them.
Command Execution Environment    The environment in which Bash executes commands that are not shell builtins.
Environment    The environment given to a command.
Exit Status    The status returned by commands and how Bash interprets it.
Signals    What happens when Bash or a command it runs receives a signal.