The following conventions are used in the synopsis of a command:
  brackets ([ and ]) indicate
  optional parts.  (In the synopsis of a Tcl command, question marks
  (?) are used instead, as is usual in Tcl.)  Braces
  ({ and }) and vertical lines
  (|) indicate that you must choose one
  alternative.  Dots (...) mean that the preceding element
  can be repeated.
 
  Where it enhances the clarity, SQL commands are preceded by the
  prompt =>, and shell commands are preceded by the
  prompt $.  Normally, prompts are not shown, though.
 
An administrator is generally a person who is in charge of installing and running the server. A user could be anyone who is using, or wants to use, any part of the PostgreSQL system. These terms should not be interpreted too narrowly; this book does not have fixed presumptions about system administration procedures.