вопрос про shell

man bash:
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SHELL BUILTIN COMMANDS
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exec [-cl] [-a name] [command [arguments]]
       If command is specified, it replaces the shell.  No new  process
       is  created.  The arguments become the arguments to command.  If
       the -l option is supplied, the shell places a dash at the begin- 
       ning of the zeroth arg passed to command.  This is what login(1)
       does.  The -c option causes command to be executed with an empty
       environment.   If  -a  is supplied, the shell passes name as the 
       zeroth argument to the executed command.  If command  cannot  be
       executed  for some reason, a non-interactive shell exits, unless 
       the shell option execfail is enabled, in which case  it  returns
       failure.   An interactive shell returns failure if the file can-
       not be executed.  If command is not specified, any  redirections
       take  effect  in  the current shell, and the return status is 0.
       If there is a redirection error, the return status is 1.
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либо fork-exec либо чисто exec