bash: Special Builtins

1 
1 4.4 Special Builtins
1 ====================
1 
1 For historical reasons, the POSIX standard has classified several
1 builtin commands as _special_.  When Bash is executing in POSIX mode,
1 the special builtins differ from other builtin commands in three
1 respects:
1 
1   1. Special builtins are found before shell functions during command
1      lookup.
1 
1   2. If a special builtin returns an error status, a non-interactive
1      shell exits.
1 
1   3. Assignment statements preceding the command stay in effect in the
1      shell environment after the command completes.
1 
1    When Bash is not executing in POSIX mode, these builtins behave no
1 differently than the rest of the Bash builtin commands.  The Bash POSIX
1 mode is described in ⇒Bash POSIX Mode.
1 
1    These are the POSIX special builtins:
1      break : . continue eval exec exit export readonly return set
1      shift trap unset
1