On Wed, 26 Oct 2022 11:03:57 +0700 Robert Elz <k...@munnari.oz.au> wrote:
> There is no bash bug here, though it could perhaps be a little > kinder to users who make this simple mistake. > > The rules for heredocs say that the end delimiter is a line. So they do. Somehow, I missed that upon my reading. > A line cannot contain an embedded newline - then it would be > two lines. > > The here doc end delimiter given after the << redirect operator > is just a shell word. Those can contain embedded newlines, either > by having an unbalanced number of unquoted single or double quote > characters, or by using $'\n' to create one. > > If the user gives such a heredoc delim after the << they have put > themselves in a situation where it is impossible to ever end > the here doc. That is until the input stream ends (EOF). > > bash could issue a warning when this occurs, rather than just > the one new versions issue when EOF is reached without the end > delimiter being located (which can happen for other reasons as well > of course). It has chosen not to. Yes, it could. While not unwelcome, the present warning came across as confusing because it expressed the would-be delimiter verbatim, newline and all. It purports to "want" something that cannnot susbequently be detected. > > Shells are allowed to extend the standard - bash has many of those > extensions. Other shells do various things when encountering a > here doc delimiter with an embedded \n - one is to look for a multi > line delimiter to end the here doc, the shell could also simply > truncate the expected end delim at the first embedded newline. > Or treat this as a syntax error. Or almost anything else. In this > case bash has chosen not to extend the standard at all - if the user > gives an end delim it is impossible to find, bash just looks for it > anyway. > > If the intent is to duplicate bash exactly (which I would not > recommend, some of what bash does is historical, and has little > tporecommend it) then this would be something that would have to > be copied. Doing so is pointless however, no real scripts, as > distinct from test cases, are going to be using a here doc > delim with embedded newlines, so this would be a case to do better. Indeed. Thanks for the clarification. -- Kerin Millar
