Under Solaris and using the Korn Shell KSH, the $- allows access to the flags setted.
Example of how it changes when setting the debug mode '-x' :
# echo $-
ismC
# set -x
# echo $-
+ echo isxmC
isxmC
# set +x
man ksh informs us that (cf.
http://www.lehman.cuny.edu/cgi-bin/man-cgi?ksh+1 for example)
" - " Correspond to the "Flags supplied to the shell on invocation or by the set command." and that "The current set of flags can be found in $- ":
Parameters Set by Shell
- Flags supplied to the shell on invocation or by
the set command.
set [ _abCefhkmnopstuvx ] [ _o option ]... [ _A name ] [ arg
... ]
The flags for this command have meaning as follows:
-A Array assignment. Unsets the variable name
and assigns values sequentially from the
list arg. If +A is used, the variable name
is not unset first.
-a All subsequent variables that are defined
are automatically exported.
-b Causes the shell to notify the user asyn-
chronously of background job completions.
The following message is written to standard
error:
"[%d]%c %s%s\n", , , , \
where the fields are as follows:
The character + identifies
the job that would be used
as a default for the fg or
bg utilities. This job can
also be specified using the
job_id %+ or %%. The charac-
ter - identifies the job
that would become the
default if the current
default job were to exit;
this job can also be speci-
fied using the job_id %-.
For other jobs, this field
is a space character. At
most one job can be identi-
fied with + and at most one
job can be identified with
-. If there is any suspended
job, then the current job is
a suspended job. If there
are at least two suspended
jobs, then the previous job
is also a suspended job.
A number that can be used to
identify the process group
to the wait, fg, bg, and
kill utilities. Using these
utilities, the job can be
identified by prefixing the
job number with %.
Unspecified.
Unspecified.
When the shell notifies the user a job has
been completed, it can remove the job's pro-
cess ID from the list of those known in the
current shell execution environment. Asyn-
chronous notification is not enabled by
default.
-C Prevents existing files from being overwrit-
ten by the shell's > redirection operator.
The >| redirection operator overrides this
noclobber option for an individual file.
-e If a command has a non-zero exit status,
executes the ERR trap, if set, and exit.
This mode is disabled while reading pro-
files.
-f Disables file name generation.
-h Each command becomes a tracked alias when
first encountered.
-k All variable assignment arguments are placed
in the environment for a command, not just
those that precede the command name.
-m Background jobs runs in a separate process
group and a line prints upon completion. The
exit status of background jobs is reported
in a completion message. On systems with job
control, this flag is turned on automati-
cally for interactive shells.
-n Reads commands and check them for syntax
errors, but do not execute them. Ignored for
interactive shells.
-o Writes the current option settings to stan-
dard output in a format that is suitable for
reinput to the shell as commands that
achieve the same option settings.
-o The following argument can be one of the
following option names:
allexport Same as -a.
errexit Same as -e.
bgnice All background jobs are run at
a lower priority. This is the
default mode.
emacs Puts you in an emacs style
in-line editor for command
entry.
gmacs Puts you in a gmacs style in-
line editor for command entry.
ignoreeof The shell does not exit onEOF.
The command exit must be used.
keyword Same as -k.
markdirs All directory names resulting
from file name generation have
a trailing / appended.
monitor Same as -m.
noclobber Prevents redirection > from
truncating existing files.
Require >| to truncate a file
when turned on. Equivalent to
-C.
noexec Same as -n.
noglob Same as -f.
nolog Do not save function defini-
tions in history file.
notify Equivalent to -b.
nounset Same as -u.
privileged Same as -p.
verbose Same as -v.
trackall Same as -h.
vi Puts you in insert mode of a
vi style in-line editor until
you hit escape character 033.
This puts you in control mode.
A return sends the line.
viraw Each character is processed as
it is typed in vi mode.
xtrace Same as -x.
If no option name is supplied, the current
option settings are printed.
-p Disables processing of the $HOME/.profile
file and uses the file /etc/suid_profile
instead of the ENV file. This mode is on
whenever the effective uid is not equal to
the real uid, or when the effective gid is
not equal to the real gid. Turning this off
causes the effective uid and gid to be set
to the real uid and gid.
-s Sorts the positional parameters lexicograph-
ically.
-t Exits after reading and executing one com-
mand.
-u Treats unset parameters as an error when
substituting.
-v Prints shell input lines as they are read.
-x Prints commands and their arguments as they
are executed.
- Turns off -x and -v flags and stops examin-
ing arguments for flags.
-- Does not change any of the flags. Useful in
setting $1 to a value beginning with -. If
no arguments follow this flag then the posi-
tional parameters are unset.
Using + rather than - causes these flags to
be turned off. These flags can also be used
upon invocation of the shell. The current
set of flags can be found in $-. Unless -A
is specified, the remaining arguments are
positional parameters and are assigned, in
order, to $1 $2 .... If no arguments are
given, the names and values of all variables
are printed on the standard output.
