No, those are attempts at speed optimizations; the description before the numbered list of XCU 2.3 has line delimiting comes first as the logical model to determine tokenizing mode. This is continued in list items 4. and 5., that substitutions shall not occur during recognition.
This makes it a requirement that a secondary pass, as the logical model, may be necessary to fully evaluate a token according to the grammar that applies for determining whether an alias name should be looked up. This model takes into account the result of a substitution may need to be classified as an assignment word or redirection when the grammar says a command prefix or keyword is the legal tokens, not a command or alias name only. This isn't obvious, but there are many scripts that rely on $CC to provide the command name for a compiler, as an example. This can't be checked whether it holds an actual name until recognition of the line as a whole has been completed. On Monday, April 20, 2020 Robert Elz <k...@munnari.oz.au> wrote: Date: Mon, 20 Apr 2020 18:01:49 +0000 (UTC) From: shwaresyst <shwares...@aol.com> Message-ID: <1837359500.1041757.1587405709...@mail.yahoo.com> | It seems to me that what is missing, in XCU 2.3.1, is a statement that use | of keywords in alias bodies is unspecified behavior. That isn't "missing" because it isn't unspecified. What's more there is no dispute at all that this works, and works in all shells. | Alias expansion occurs after this line is identified, No, it doesn't. It occurs immediately after a word has been recognised in the command position - just the same as keyword recognition - and when a previous alias expansion has caused the next word to be a potential alias. Alias expansion (XCU 2.3.1) is in the Token recognition (XCU 2.3) section of the standard for a reason, it is not a word expansion (XCU 2.6)). But this is a general discussion of aliases, which is also not the point of my query (unless this turns into a "remove aliases entirely" discussion) which was very specific to alias recognition in command substitutions that are quoted. Joseph's message helps provide context, and it may be that now the "historically shells have not done this" is nolonger true, and the standard should revert to its earlier form. kre
