plus if an alias definition ends with a space , when in use , further aliases may get resolved ( substituded , before parsing code further )
On Fri, Feb 17, 2023, 5:37 PM Dale R. Worley <wor...@alum.mit.edu> wrote: > Chet Ramey <chet.ra...@case.edu> writes: > > On 2/14/23 2:58 PM, Dale R. Worley wrote: > >>>> Looking at the manual page, it says > >>>> > >>>> ALIASES > >>>> Aliases allow a string to be substituted for a word when it > is used as > >>>> the first word of a simple command. > >> > >> Martin suggested (but IIUC didn't sent to this list): > >>> "Beginning of a simple command" should probably be replaced by > something > >>> more along the lines of "beginning of any command that does not start > with > >>> a keyword (such as "while", "if", "case", etc) or assignment. > >> > >> Though I think by "keyword" he means "reserved word". > > > > I think the issue is that he's applying a grammar interpretation (simple > > command) to something that is a completely lexical operation. Alias > > expansion happens in the lexical analyzer, and it happens when a token > > can potentially be the first word of a simple command. > > Well, (1) I'm looking at it based on the *documentation*, which says > "simple command". And my essential point is that the documentation > should be adjusted to handle this specific case, viz. alias-izing the > name of a function that one wants to define without a "function" > reserved word. Let me reiterate that, for a lot of these odd points, > I'm much more fussy that the documentation describes what Bash does than > that I particularly prefer the choice the Bash implementation does. > > All of that is qualified by (2) The actual workings of aliases are > complicated, and as you note, in the lexing rather than the parsing. > But contrary to my point (1), I'm willing to tell anyone who uses > aliases to modify things that are grammatically salient (rather than > command names) that they are in "here be dragons" territory, it's their > problem if the documentation doesn't clearly delineate what will happen, > and they need to test examples to tell. > > So then, (3) What is a practical change to the manual page? The first > three sentences in version 5.1.0(1) are: > > ALIASES > Aliases allow a string to be substituted for a word when it is > used as > the first word of a simple command. The shell maintains a > list of > aliases that may be set and unset with the alias and unalias > builtin > commands (see SHELL BUILTIN COMMANDS below). The first word of > each > simple command, if unquoted, is checked to see if it has an > alias. > > I think this change covers the case we're talking about, clarifies the > second sentence a bit, and seems to be well-aligned with the more > detailed truth: > > Aliases allow a string to be substituted for a word when it is > used as the first word of a simple command. The alias and > unalias builtin commands (see SHELL BUILTIN COMMANDS below) set > and unset aliases. Reserved words may not be aliased, but all > other tokens may. A word in a position which could start a > simple command, if unquoted, is checked to see if it has an > alias. (A side effect is that the function name in a function > definition that does not start with the "function" keyword is > checked for alias expansion.) > > Dale > >
