sourcepath
If set, the source builtin uses the value of PATH to find the directory containing the file supplied as an argument. This option is enabled by default. xpg_echo
If set, the echo builtin expands backslash-escape sequences by de- fault.
The return status when listing options is zero if all optnames are enabled, non- zero otherwise. When setting or unsetting options, the return status is zero unless an optname is not a valid shell option.
4.4 Special Builtins
For historical reasons, the posix standard has classified several builtin commands as spe- cial. When Bash is executing in posix mode, the special builtins differ from other builtin commands in three respects:
1. Special builtins are found before shell functions during command lookup.
2. If a special builtin returns an error status, a non-interactive shell exits.
3. Assignment statements preceding the command stay in effect in the shell environment after the command completes.
When Bash is not executing in posix mode, these builtins behave no differently than the rest of the Bash builtin commands. The Bash posix mode is described in Section 6.11
[Bash POSIX Mode], page 94.
These are the posix special builtins: break : . continue eval exec exit export readonly return set shift trap unset