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Definition of $-

 
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Top Forums UNIX for Dummies Questions & Answers Definition of $-
# 8  
Old 06-09-2009
The following applies to vanila ksh93t. The set of possible characters retuned by $- is:
Code:
DircabefhkmnpstuvxBCGEl

The meaning of these can be mostly inferred from the following defines which match the order of the above characters
Code:
SH_DICTIONARY, SH_INTERACTIVE, SH_RESTRICTED, SH_CFLAG,
SH_ALLEXPORT, SH_NOTIFY, SH_ERREXIT, SH_NOGLOB, SH_TRACKALL,
SH_KEYWORD, SH_MONITOR, SH_NOEXEC, SH_PRIVILEGED, SH_SFLAG, SH_TFLAG,
SH_NOUNSET, SH_VERBOSE,  SH_XTRACE, SH_BRACEEXPAND, SH_NOCLOBBER,
SH_GLOBSTARS, SH_RC, SH_LOGIN_SHELL

where SH_CFLAG, i.e. 'c', is set if ksh93 is involved with a "-c cmdstring" command line option.
# 9  
Old 06-09-2009
Code:
/home/jmcnama> echo $-
isam
/home/jmcnama> ksh -c
echo $-
shc
exit
/home/jmcnama> echo $-
isam
/home/jmcnama> set -v
/home/jmcnama> echo $-
echo $-
ivsam
/home/jmcnama>

$- with a "c" in it means the shell was invoked with -c. Period. It does not tell you more than that. As you can see $- shows both invocation options, plus any options you set later on, in this example verbose was turned on interactively.

$- reflects BOTH options set at shell invocation and set later on. It is there to let you know what your runtime environment is like, -v for example, changes the way the running script appears to the user.
# 10  
Old 06-11-2009
Ok, I guess I was wrong. That was exactly what I was looking for. The last two posts have given enough detail to explain to me what I was unable to find in any of the man pages.

So now I would like to know how you found this information. I have looked at both the ksh and bash man pages in detail and cannot find anything that explains the association of the individual letters with these options (at least for many of them). In fact, in the man pages I'm looking at on Solaris 10, there are no options that even begin with "SH_". And many of the options are ambiguous if you simply look at the first letter (i.e. hashall, histexpand, history; or emacs, errtrace; or physical, pipefail, posix, privileged; etc.)

Anyway, thanks for the info.
# 11  
Old 06-11-2009
For ksh: the man page for ksh explains them. Look for the set keyword. ksh88 is what I showed you - this is what Solaris supports by default. fpMurphy showed you ksh93 - which is an add-on that you used to have to purchase separately.
There is also pdksh[number] a public domain version with newer features.
Code:
echo $SHELL

will tell you which one you are running.

The point is - there are some very different new features in ksh93, many of which are involved in PITA part of shell programming - string splitting, date arithmetic, etc. So your results may vary depending on your shell version.
Last edited by jim mcnamara; 06-11-2009 at 11:52 AM..
# 12  
Old 06-11-2009
The '$-' (and its friends $$, $? etc) are described in 'man ksh' under the header 'Parameters Set by Shell' (on Solaris). Here's the snippet:
Code:
  Parameters Set by Shell
     The following parameters are automatically set by the shell:

     #     The number of positional parameters in decimal.

     -     Flags supplied to the shell on invocation  or  by  the
           set command.

     ?     The decimal value returned by the last  executed  com-
           mand.

For the 'set -v' (and its friends), 'man ksh' and search for the 'Special Commands' header (on Solaris again). Here's the snippet of that:
Code:
Special Commands
...........
...........
     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.

# 13  
Old 06-11-2009
Quote:
Originally Posted by sszd
So now I would like to know how you found this information. I have looked at both the ksh and bash man pages in detail and cannot find anything that explains the association of the individual letters with these options (at least for many of them). In fact, in the man pages I'm looking at on Solaris 10, there are no options that even begin with "SH_". And many of the options are ambiguous if you simply look at the first letter (i.e. hashall, histexpand, history; or emacs, errtrace; or physical, pipefail, posix, privileged; etc.)
The information I provided is based on my knowledge of the ksh93 source code. It is not really documented fully in the man page or elsewhere.

Note that this information only pertains to ksh93 and not to pdksh, ksh88 or bash.
 
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