next set of documentation updates (word splitting), rearrange a test in readline's tilde expansion to avoid touching uninitialized data

doc/bash.1

@@ -5,14 +5,14 @@
 .\"	Case Western Reserve University
 .\"	chet.ramey@case.edu
 .\"
-.\"	Last Change: Tue Oct 15 16:53:49 EDT 2024
+.\"	Last Change: Sun Oct 20 12:31:15 EDT 2024
 .\"
 .\" bash_builtins, strip all but Built-Ins section
 .\" avoid a warning about an undefined register
 .\" .if !rzY .nr zY 0
 .if \n(zZ=1 .ig zZ
 .if \n(zY=1 .ig zY
-.TH BASH 1 "2024 October 15" "GNU Bash 5.3"
+.TH BASH 1 "2024 October 20" "GNU Bash 5.3"
 .\"
 .ie \n(.g \{\
 .ds ' \(aq
@@ -483,6 +483,10 @@ document.
 .B blank
 A space or tab.
 .TP
+.B whitespace
+A character belonging to the \fBspace\fP character class in the
+current locale, or for which \fIisspace\fP(3) returns true.
+.TP
 .B word
 A sequence of characters considered as a single unit by the shell.
 Also known as a
@@ -4015,92 +4019,77 @@ and
 arithmetic expansion
 that did not occur within double quotes for
 .IR "word splitting" .
+Words that were not expanded are not split.
 .PP
 The shell treats each character of
 .SM
 .B IFS
-as a delimiter, and splits the results of the other
-expansions into words using these characters as field terminators.
+as a delimiter,
+and splits the results of the other expansions into words
+using these characters as field terminators.
+.PP
+An \fIIFS whitespace\fP character is whitespace as defined above
+(see \fBDefinitions\fP) that appears in the value of
+.SM
+.BR IFS .
+Space, tab, and newline are always considered IFS whitespace, even
+if they don't appear in the locale's \fBspace\fP category.
 .PP
 If
 .SM
 .B IFS
-is unset, or its
-value is exactly
+is unset, field splitting acts as if its value were
 .BR <space><tab><newline> ,
-the default, then
-sequences of
-.BR space ,
-.BR tab ,
-and
-.B newline
-at the beginning and end of the results of the previous
-expansions are ignored, and
-any sequence of
+and treats these characters as IFS whitespace.
+If the value of
 .SM
 .B IFS
-characters not at the beginning or end delimits words.
-If
-.SM
-.B IFS
-has a value other than the default, then sequences of
-the whitespace characters
-.BR space ,
-.BR tab ,
-and
-.B newline
-present in the value of
-.SM
-.B IFS
-(an
-.SM
-.B IFS
-whitespace character)
-are ignored at the beginning and end of the word.
-Any character in
-.SM
-.B IFS
-that is not
-.SM
-.B IFS
-whitespace, along with any adjacent
-.SM
-.B IFS
-whitespace characters, delimits a field.
-A sequence of
-.SM
-.B IFS
-whitespace characters is also treated as a delimiter.
+is null, no word splitting occurs,
+but implicit null arguments (see below) are still removed.
+.PP
+Word splitting begins by removing sequences of IFS whitespace characters
+from the beginning and end of the results of the previous expansions,
+then splits the remaining words.
 .PP
 If the value of
 .SM
 .B IFS
-is null, no word splitting occurs.
+consists solely of IFS whitespace,
+any sequence of IFS whitespace characters delimits a field,
+so a field consists of characters that are not unquoted IFS
+whitespace, and null fields result only from quoting.
+.PP
 If
 .SM
 .B IFS
-is unset, word splitting behaves as if it contained the default value
-of
-.BR <space><tab><newline> .
+contains a non-whitespace character, then any character in
+the value of
+.SM
+.B IFS
+that is not IFS whitespace,
+along with any adjacent IFS whitespace characters, delimits a field.
+This means that adjacent non-IFS-whitespace delimiters produce a
+null field.
+A sequence of IFS whitespace characters also delimits a field.
 .PP
 Explicit null arguments (\^\fB\*"\^\*"\fP or
 \^\fB\*'\^\*'\fP\^) are retained
 and passed to commands as empty strings.
 Unquoted implicit null arguments, resulting from the expansion of
 parameters that have no values, are removed.
-If a parameter with no value is expanded within double quotes, a
-null argument results and is retained
-and passed to a command as an empty string.
+Expanding a  parameter with no value within double quotes
+produces a null field,
+which is retained and passed to a command as an empty string.
+.PP
 When a quoted null argument appears as part of a word whose expansion is
-non-null, the null argument is removed.
+non-null, word splitting removes the null argument portion,
+leaving the non-null expansion.
 That is, the word
 .Q "\-d\*'\^\*'"
 becomes
 .Q \-d
 after word splitting and null argument removal.
-.PP
-Note that if no expansion occurs, no splitting is performed.
-.SS Pathname Expansion
+.SS "Pathname Expansion"
 After word splitting,
 unless the
 .B \-f