Chet Ramey wrote: > Bash and csh both permit backslash to inhibit history expansion when in > double quotes.
If a printable character has special meaning in syntax for representing data strings, then in any situation where it's special, it is expected to be possible to disable that specialness by prefixing the special character with some escape character, commonly a backslash. The combination escape-followed-by-special literally represents the special character. This rule is essentially universal in the *nix world. There is a good reason for it: it's predictable, easy to follow, minimizes surprises, and doesn't add restrictions on the data that can be represented. Exceptions should not be made without careful thought. Certainly not inadvertently and carelessly as a result of a bug. And even with the specialness of bang turned off, it still doesn't work right: [EMAIL PROTECTED]:~> set +H [EMAIL PROTECTED]:~> echo "hi there!" hi there! [EMAIL PROTECTED]:~> echo "hi there\!" hi there\! [EMAIL PROTECTED]:~> echo hi there! hi there! [EMAIL PROTECTED]:~> echo hi there\! hi there! So tell me, how do you rationalize that in terms of history expansion, in a situation where history expansion has nothing to do with it? > Later on, in the subsequent word expansion steps, bash and csh differ. csh > allows backslash to act as an escape character when it precedes `!' in a > double-quoted string, and removes it. Bash allows backslash to act as an > escape character only when it precedes the characters so specified in the > Posix standard, and `!' is not one of those, so bash leaves the \! intact. In that case, you need to fix the documentation, because that's not what bashref section 9.3 says. Let me draw your attention again to the relevant sentence: ³Only \¹ and '¹ may be used to escape the history expansion character². No mention in there of any difference in behaviour due to the presence of double-quotes. Therefore if your current explanation is to be accepted, then that description needs some expansion. Either fix the code to reflect the documentation, or fix the documentation to reflect the code. What's it going to be?
