The command 'set -o' shows the current shell options in an unspecified
format. Less well-known is the variant 'set +o', which should output the
current shell options "in a format that is suitable for reinput to the
shell as commands that achieve the same options settings".[*]
That means it should be possible to do something like
save_options=$(set +o)
then change some options, then later restore the shell options with
eval "$save_options"
On all pdksh variants (as well as zsh), 'set +o' is currently inadequate
for that purpose because it only outputs the currently active shell
options, and not the inactive ones.
Even the old ksh88, which pdksh is a clone of (and on which most of
POSIX is based), acts correctly in this regard.
This simple patch makes 'set +o' compatible with the POSIX spec.
Thanks,
- M.
[*]
http://pubs.opengroup.org/onlinepubs/9699919799/utilities/V3_chap02.html#tag_18_25_03
(scroll down to '+o')
Index: bin/ksh/misc.c
===================================================================
RCS file: /cvs/src/bin/ksh/misc.c,v
retrieving revision 1.53
diff -u -p -u -r1.53 misc.c
--- bin/ksh/misc.c 21 Dec 2015 04:57:50 -0000 1.53
+++ bin/ksh/misc.c 6 Mar 2016 04:27:20 -0000
@@ -240,8 +240,10 @@ printoptions(int verbose)
/* short version ala ksh93 */
shprintf("set");
for (i = 0; i < NELEM(options); i++)
- if (Flag(i) && options[i].name)
- shprintf(" -o %s", options[i].name);
+ if (options[i].name)
+ shprintf(" %co %s",
+ Flag(i) ? '-' : '+',
+ options[i].name);
shprintf("\n");
}
}
Index: bin/ksh/ksh.1
===================================================================
RCS file: /cvs/src/bin/ksh/ksh.1,v
retrieving revision 1.175
diff -u -p -u -r1.175 ksh.1
--- bin/ksh/ksh.1 4 Mar 2016 18:16:50 -0000 1.175
+++ bin/ksh/ksh.1 6 Mar 2016 04:27:20 -0000
@@ -3734,7 +3734,8 @@ options (with single letter names) can b
.Ic set Fl o
with no option name will list all the options and whether each is on or off;
.Ic set +o
-will print the long names of all options that are currently on.
+will print the current shell options in the form of a command that
+can be reinput to the shell to achieve the same options settings.
.Pp
Remaining arguments, if any, are positional parameters and are assigned, in
order, to the positional parameters (i.e. $1, $2, etc.).
