> > Current bash.xml accepts (a), but not (b). The single qoute is > > the start of string highlight. It's also not just the backtick > > block, but the backtick block inside of a double quote string > > block - and vice versa.
First, be aware that `` in bash 3.1 was buggy, so you should upgrade to bash 3.2 rather than trying to figure out how the broken 3.1 parsing worked. > > > > x="`echo \"'\\\"\"`" is valid > > My bash highlighter thinks this is invalid. So does my brain. However > bash seems OK with it. Why, I wonder? Maybe I am not clear on the > expansion rules in this instance. > This is valid. According to POSIX, the double quoted string is terminated by the matching unquoted double quote, and within that string, the `` string is executed on the contents of the `` with the \ quotes before any $, `, ", \, and newline removed. So the result is that you are executing the command: `echo "'\""` Then, according to `` rules, $, `, and \ are special (but not "), so the subshell sees the command: echo "'\"" which is valid, and results in '" being assigned to x. > > x=`echo \"'\\\"\"` isn't > > Ditto, except bash also (correctly IMO) doesn't like it. Here, there is no surrounding "" to strip leading \ quotes special to "". So you are executing the command `echo \"'\\\"\"` and according to the rules of ``, the subshell sees: echo \"'\\"\" which indeed is a syntax error. > > > The other way around: > > > > x=`echo "'\""` is valid Valid. The subshell sees: echo "'\"" and x is assigned '" > > > > x="`echo "'\""`" isn't > > > > but both are highlighted as valid. Invalid. The "" ends at the first unquoted ", but that meant that you had an unpaired `, so bash is allowed to reject this. The difference was that by adding "" around ``, you have to also add \ escapes around characters special to "". > > That's odd, because all of the following are valid: > > echo "'\"" Valid. > echo `echo "'\""` Valid. The inner echo results in the three characters '"<newline>, then the `` strips the newline, and since this was the expansion of ``, no further quoting is needed and the outer echo results in '" again. > x="$(echo "'\"")" <-- this should be syntactically equivalent?! $() has different rules than ``. Inside $(), any valid script is allowed, and by itself, echo "'\"" is a valid script. And inside "$()", the rules are explicit that the contents of the $() are not subject to normal "" escapes, but that the closing ) is found by a recursive parse. > > ...so this feels like a bug in bash. No, bash is correct. `` and $() are different, and the rules for "``" are different from "$()". And if it weren't for the fact that Solaris /bin/sh still doesn't understand $() which hampers its portable use, I would gladly ditch `` for the nicer semantics of $(). -- Eric Blake -- View this message in context: http://www.nabble.com/Re%3A--Bug-103756--kate%3A-syntax-highlighting-error%3A-bash-and-escaped-quotes-tf3507272.html#a9800902 Sent from the Gnu - Bash mailing list archive at Nabble.com. _______________________________________________ Bug-bash mailing list Bug-bash@gnu.org http://lists.gnu.org/mailman/listinfo/bug-bash
