On 2016-04-07, Christian Weisgerber <[email protected]> wrote:
> Let's illustrate the issue:
>
> $ sh -c 'echo "`echo \"hi\"`"'
> hi
> $ sh -o posix -c 'echo "`echo \"hi\"`"'
> "hi"
>
> I'll just quote ksh.1:
>
> o Occurrences of \" inside double quoted `..` command substitutions.
> In POSIX mode, the \" is interpreted when the command is interpreted;
> in non-POSIX mode, the backslash is stripped before the command
> substitution is interpreted. For example, echo "`echo \"hi\"`"
> produces ``"hi"'' in POSIX mode, ``hi'' in non-POSIX mode. To avoid
> problems, use the $(...) form of command substitution.
>
> From time to time there's a configure script in ports that sets -o
> posix but expects the other behavior, because other popular shells
> do not share this interpretation of what POSIX mandates. bash,
> whether in POSIX mode or not, and FreeBSD's sh always strip the
> backslashes.
>
> On reading the POSIX text, I find the ksh author's interpretation
> far-fetched. See also:
> http://austingroupbugs.net/view.php?id=1015
>
> Regardless of what you contend the standard text says, I think it
> is clear that the other interpretation has won out in practice and
> I propose to align our ksh with that:
This has now successfully passed a bulk package build.
> Index: lex.c
>===================================================================
> RCS file: /cvs/src/bin/ksh/lex.c,v
> retrieving revision 1.68
> diff -u -p -r1.68 lex.c
> --- lex.c 4 Mar 2016 09:37:23 -0000 1.68
> +++ lex.c 7 Apr 2016 16:18:13 -0000
> @@ -427,40 +427,22 @@ yylex(int cf)
> /* Need to know if we are inside double quotes
> * since sh/at&t-ksh translate the \" to " in
> * "`..\"..`".
> - * This is not done in posix mode (section
> - * 3.2.3, Double Quotes: "The backquote shall
> - * retain its special meaning introducing the
> - * other form of command substitution (see
> - * 3.6.3). The portion of the quoted string
> - * from the initial backquote and the
> - * characters up to the next backquote that
> - * is not preceded by a backslash (having
> - * escape characters removed) defines that
> - * command whose output replaces `...` when
> - * the word is expanded."
> - * Section 3.6.3, Command Substitution:
> - * "Within the backquoted style of command
> - * substitution, backslash shall retain its
> - * literal meaning, except when followed by
> - * $ ` \.").
> */
> statep->ls_sbquote.indquotes = 0;
> - if (!Flag(FPOSIX)) {
> - Lex_state *s = statep;
> - Lex_state *base = state_info.base;
> - while (1) {
> - for (; s != base; s--) {
> - if (s->ls_state ==
> SDQUOTE) {
> -
> statep->ls_sbquote.indquotes = 1;
> - break;
> - }
> - }
> - if (s != base)
> - break;
> - if (!(s = s->ls_info.base))
> + Lex_state *s = statep;
> + Lex_state *base = state_info.base;
> + while (1) {
> + for (; s != base; s--) {
> + if (s->ls_state == SDQUOTE) {
> +
> statep->ls_sbquote.indquotes = 1;
> break;
> - base = s-- - STATE_BSIZE;
> + }
> }
> + if (s != base)
> + break;
> + if (!(s = s->ls_info.base))
> + break;
> + base = s-- - STATE_BSIZE;
> }
> break;
> default:
> Index: ksh.1
>===================================================================
> RCS file: /cvs/src/bin/ksh/ksh.1,v
> retrieving revision 1.178
> diff -u -p -r1.178 ksh.1
> --- ksh.1 21 Mar 2016 13:35:00 -0000 1.178
> +++ ksh.1 7 Apr 2016 16:10:58 -0000
> @@ -822,12 +822,6 @@ the
> and the newline are stripped; otherwise, both the
> .Ql \e
> and the character following are unchanged.
> -.Pp
> -.Sy Note :
> -See
> -.Sx POSIX mode
> -below for a special rule regarding
> -differences in quoting when the shell is in POSIX mode.
> .Ss Aliases
> There are two types of aliases: normal command aliases and tracked aliases.
> Command aliases are normally used as a short hand for a long or often used
> @@ -2472,27 +2466,6 @@ The following is a list of things that a
> .Ic posix
> option:
> .Bl -bullet
> -.It
> -Occurrences of
> -.Ic \e\&"
> -inside double quoted
> -.Ic `..`
> -command substitutions.
> -In POSIX mode, the
> -.Ic \e\&"
> -is interpreted when the command is interpreted;
> -in non-POSIX mode,
> -the backslash is stripped before the command substitution is interpreted.
> -For example,
> -.Ic echo \&"`echo \e\&"hi\e\&"`\&"
> -produces
> -.Dq \&"hi\&"
> -in POSIX mode,
> -.Dq hi
> -in non-POSIX mode.
> -To avoid problems, use the
> -.Ic $(...)\&
> -form of command substitution.
> .It
> .Ic kill -l
> output.
--
Christian "naddy" Weisgerber [email protected]
