Re: Question on $IFS related differences (Was: Question on $@ vs $@$@)

[Steffen Nurpmeso]

Chet Ramey wrote in
 <b72edbc9-d336-4391-98a9-37c670afa435@case.edu>:
 |On 9/18/24 1:05 AM, Oğuz wrote:
 |> On Wed, Sep 18, 2024 at 4:19 AM Steffen Nurpmeso <steffen@sdaoden.eu> \
 |> wrote:
 |> It boils down to this:
 |> 
 |>    f(){ echo $#;}; set "" "" ""; IFS=x; f $*
 |> 
 |> bash, NetBSD and FreeBSD sh, and ksh88 all agree and print 2. pdksh
 |> prints 3 but mksh and oksh print 1. dash, ksh93, yash, and zsh print
 |> 0.
 |
 |It's an implementation difference.
 |
 |The shells that print `0' treat the `may' as `shall' in this sentence from
 |
 |https://pubs.opengroup.org/onlinepubs/9799919799/utilities/V3_chap02.htm\
 |l#tag_19_05_02
 |
 |"When the expansion occurs in a context where field splitting will be
 |performed, any empty fields may be discarded and each of the non-empty
 |fields shall be further split as described in 2.6.5 Field Splitting."
 |
 |So they immediately expand the $* to nothing.
 |
 |The shells that print `2' don't immediately discard the empty fields and
 |separate them with the first character of IFS. After quote removal and
 |removing the empty fields, since the individual words in $* are subject
 |to additional expansion, you're left with `xx'. When you split that,
 |you get two empty fields.

Thank you for this analysis.
(Here it is just a shell expander, ie, it acts like a format
string expander, and these steps you include, namely "quote
removal" etc, are nothing i can or want to mimic.)

 |I'm not sure what's going on with the shells that print `1' unless they
 |somehow don't use the first character of IFS to separate the arguments
 |and let multiple sequential delimiters terminate the first field.
 |
 |I assume that pdksh just expands each positional parameter to a quoted
 |empty string and passes them all to f.

--steffen
|
|Der Kragenbaer,                The moon bear,
|der holt sich munter           he cheerfully and one by one
|einen nach dem anderen runter  wa.ks himself off
|(By Robert Gernhardt)