set(1posix) - set or unset options and positional parameters
-a     When this option is on, the export attribute shall be set for each variable to which an assignment
       is  performed;  see  the  Base  Definitions volume of IEEE Std 1003.1-2001, Section 4.21, Variable
       Assignment. If the assignment precedes a utility name in a command, the export attribute shall not
       persist  in the current execution environment after the utility completes, with the exception that
       preceding one of the special built-in utilities causes the export attribute to persist  after  the
       built-in  has  completed.  If the assignment does not precede a utility name in the command, or if
       the assignment is a result of the operation of the getopts or read utilities, the export attribute
       shall persist until the variable is unset.
-b     This  option  shall  be  supported  if  the implementation supports the User Portability Utilities
       option. It shall cause the shell to notify the user asynchronously of background job  completions.
       The following message is written to standard error:
-C     (Uppercase C.) Prevent existing files from  being  overwritten  by  the  shell's  '>'  redirection
       operator  (see  Redirecting  Output ); the ">|" redirection operator shall override this noclobber
       option for an individual file.
-e     When this option is on, if a simple command fails for any of the reasons listed in Consequences of
       Shell  Errors or returns an exit status value >0, and is not part of the compound list following a
       while, until, or if keyword, and is not a part of an AND  or  OR  list,  and  is  not  a  pipeline
       preceded by the ! reserved word, then the shell shall immediately exit.
-f     The shell shall disable pathname expansion.
-h     Locate  and  remember utilities invoked by functions as those functions are defined (the utilities
       are normally located when the function is executed).
-m     This option shall be supported if the  implementation  supports  the  User  Portability  Utilities
       option.  All  jobs shall be run in their own process groups. Immediately before the shell issues a
       prompt after completion of the background  job,  a  message  reporting  the  exit  status  of  the
       background  job  shall  be  written  to standard error. If a foreground job stops, the shell shall
       write a message to standard error to that effect, formatted as described by the jobs utility.   In
       addition, if a job changes status other than exiting (for example, if it stops for input or output
       or is stopped by a SIGSTOP signal), the shell shall write a similar message immediately  prior  to
       writing the next prompt. This option is enabled by default for interactive shells.
-n     The  shell  shall  read  commands  but  does not execute them; this can be used to check for shell
       script syntax errors. An interactive shell may ignore this option.
-o     Write the current settings of the options to standard output in an unspecified format.

+o     Write the current option settings to standard output in a format that is suitable for  reinput  to
       the shell as commands that achieve the same options settings.
-o  option
-u     The shell shall write a message to standard error when it tries to expand a variable that  is  not
       set and immediately exit. An interactive shell shall not exit.
-v     The shell shall write its input to standard error as it is read.
-x     The  shell shall write to standard error a trace for each command after it expands the command and
       before it executes it. It is unspecified whether the command that turns tracing off is traced.