On 1.8. 15:12, Greg Wooledge wrote:
On Wed, Aug 01, 2018 at 02:43:27PM +0300, Ilkka Virta wrote:
On both Bash 4.4.12(1)-release and 5.0.0(1)-alpha, a subarray slice like
${a[@]:0} expands to just one word if unquoted (and if IFS doesn't
contain a space):
This just reinforces the point that unquoted $@ or $* (or the array
equivalent) is a bug in the script. It gives unpredictable results.
Unquoted $* seems well-defined in Bash's reference manual:
($*) Expands to the positional parameters, starting from one. When the
expansion is not within double quotes, each positional parameter
expands to a separate word.
The reference doesn't really say anything about an unquoted $@, but then
there's the POSIX definition which should be well-defined in this case,
since clearly field-splitting should be performed here.
@: Expands to the positional parameters, starting from one, initially
producing 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 Field Splitting.
Now, of course POSIX doesn't say anything about arrays or the
subarray/slice notation, but then Bash's reference mentions that
[@] and [*] are supposed to be analoguous to $@ and $*, and the
description of ${parameter:offset:length} doesn't say that
${array[@]:n:m} would act differently from ${array[@]} let alone
differently from ${@:n:m}.
Instead, the wording of the subarray/slice expansion is similar for both
${@:n:m} and ${array[@]:n:m}:
${parameter:offset:length}
If parameter is ‘@’, the result is length positional parameters
beginning at offset.
If parameter is an indexed array name subscripted by ‘@’ or ‘*’, the
result is the length members of the array beginning with
${parameter[offset]}.
It doesn't say what's done with those parameters or array members, but
if the behaviour is supposed to be different between these two cases,
it's not documented.
--
Ilkka Virta / itvi...@iki.fi
