The following issue has been SUBMITTED.
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https://www.austingroupbugs.net/view.php?id=1915
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Reported By: steffen
Assigned To:
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Project: 1003.1(2016/18)/Issue7+TC2
Issue ID: 1915
Category: Shell and Utilities
Type: Clarification Requested
Severity: Editorial
Priority: normal
Status: New
Name: steffen
Organization:
User Reference:
Section: 2.5.2
Page Number: 2479
Line Number: 80382
Interp Status: ---
Final Accepted Text:
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Date Submitted: 2025-03-17 19:17 UTC
Last Modified: 2025-03-17 19:17 UTC
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Summary: clarification of 2.6.5 field splitting of 2.5.2
special parameter $*
Description:
I was implementing a shell expression parser.
It was impossible to generate $* splitting compatible compatible with bash,
NetBSD sh and NetBSD ksh.
The standard defines (p. 2479, lines 80382 ff.)
<blockquote>
[.]one field for
each positional parameter that is set. 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 Section 2.6.5.
</blockquote>
So in an example
<code>
a() {
echo $#,1="$1"/$1,2="$2"/$2,3="$3"/$3,4="$4"
echo $#,'*'="$*"/$*,
}
set -- '' 'a' ''
for f in ' ' '' : ': ' ' :'; do
IFS=$f ; echo "$*"$* $*; a "$*"$* $*;unset IFS
done
</code>
my parser was en par with the mentioned shells except for
<code>
--- .1 2025-03-15 23:38:31.359307576 +0100
+++ .2 2025-03-15 23:38:32.715974215 +0100
@@ -6,10 +6,10 @@ a a a$
3,*=aaa/a a a,$
:a: a a$
4,1=:a:/ a ,2=a/a,3=/,4=a$
-4,*=:a::a::a/ a a a,$
+4,*=:a::a::a/ a a a,$
:a: a a$
4,1=:a:/ a ,2=a/a,3=/,4=a$
-4,*=:a::a::a/ a a a,$
+4,*=:a::a::a/ a a a,$
a a a$
3,1= a / a ,2=a/a,3=a/a,4=$
3,*= a a a/ a a a,$
</code>
After that many months i did not give up and wrote to kre@ and on the bash-bug
list:
<code>
By the very meaning of this [POSIX words] the fields are split individually,
*first*. This is exactly what i do.
Hence
echo $#,1="$1"/$1,2="$2"/$2,3="$3"/$3,4="$4"
->
4,1=:a:/ a ,2=a/a,3=/,4=a
becomes
:a: -> '' + a
a -> a
'' -> discarded (but remembered as it separates fields)
a -> a
becomes, with IFS=:, when actually creating the argument
:a:a::a
becomes the actual argument
< a a a>
</code>
Long story short (initial typo corrected):
<code>
+ /* In order to be compatible with bash, NetBSD sh and
NetBSD ksh, at minimum, we need to
+ * deviate from POSIX standardized behaviour, and
field split the quoted variant instead!
+ * This applies to $@ as well as $* */
+ if(*spcp->spc_ifs != '\0' &&
!su_cs_is_space(*spcp->spc_ifs)){
+ cp = n_var_vlook(n_star, TRU1);
+ goto jfs_split;
+ }
+
+ /* In all other cases individually field split the
expanded parameters */
</code>
Ie, the mentioned shells use the *quoted* variant of $* to perform the expansion
in the mentioned case.
This seems to be the case for multiple decades, if not ever.
Desired Action:
Please clarify whether POSIX *really* meant what it says in *all* cases, whether
the text is an omission of taking over application behavior into the first
standard version.
Or, whether the above special case for non-(IFS-)WS byte in IFS[0] is a regular
desired implementation detail.
(maybe reorder mantis layout so section etc are at the top again?)
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Issue History
Date Modified Username Field Change
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2025-03-17 19:17 steffen New Issue
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