[PATCH] make 'set +o' useful and POSIX compatible

[PATCH] make 'set +o' useful and POSIX compatible

[Martijn Dekker]

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

        save_options=$(set +o)

then change some options, then later restore the shell options with

        eval "$save_options"

On zsh (as well as all pdksh variants), 'set +o' is currently inadequate
for that purpose because it only outputs the currently active shell
options, and not the inactive ones.

The zshbuiltins(1) man page also implies that 'set +o' should print the
complete current option states.

This is my first time trying my hand at a zsh patch.

Thanks,

- M.

[*]
http://pubs.opengroup.org/onlinepubs/9699919799/utilities/V3_chap02.html#tag_18_25_03
    (scroll down to '+o')

diff --git a/Src/options.c b/Src/options.c
index 17c46c3..18619c8 100644
--- a/Src/options.c
+++ b/Src/options.c
@@ -847,9 +847,10 @@ printoptionnodestate(HashNode hn, int hadplus)
     int optno = on->optno;

     if (hadplus) {
-        if (defset(on, emulation) != isset(optno))
-	    printf("set -o %s%s\n", defset(on, emulation) ?
-		   "no" : "", on->node.nam);
+	printf("set %co %s%s\n",
+	       defset(on, emulation) != isset(optno) ? '-' : '+',
+	       defset(on, emulation) ? "no" : "",
+	       on->node.nam);
     } else {
 	if (defset(on, emulation))
 	    printf("no%-19s %s\n", on->node.nam, isset(optno) ? "off" : "on");

Re: [PATCH] make 'set +o' useful and POSIX compatible

[Martijn Dekker]

Martijn Dekker schreef op 27-02-16 om 04:11:
> That means it should be possible to do
> 
>         save_options=$(set +o)
> 
> then change some options, then later restore the shell options with
> 
>         eval "$save_options"

Hmm. There is still a problem with this.

Two options are turned off in subshells, so the command substitution
subshell $(set +o) will not store the output you want.

$ set +o >1
$ (set +o) >2
$ diff 1 2
116c116
< set -o monitor
---
> set +o monitor
177c177
< set -o zle
---
> set +o zle

This only seems to be relevant on interactive shells though, as
'monitor' and 'zle' are turned off in scripts.

- M.

Re: [PATCH] make 'set +o' useful and POSIX compatible

[Bart Schaefer]

On Feb 27,  4:11am, Martijn Dekker wrote:
}
} On zsh (as well as all pdksh variants), 'set +o' is currently inadequate
} for that purpose because it only outputs the currently active shell
} options, and not the inactive ones.

This is almost certainly not coincidental.  In the early years of zsh
development, ksh was only available on closed-source UNIX platforms,
so any ksh-isms that were incorporated were either derived from reading
man pages (which led by misunderstanding to the "coproc" command and
an unusual syntax for writing base-N values in arithmetic context) or
borrowed from pdksh.

I don't see any reason not to accept this patch.