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Groups > gnu.bash.bug > #12132

${1+"$@"} does not generate multiple words if IFS is empty

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Configuration Information [Automatically generated, do not change]:
Machine: x86_64
OS: darwin11.4.2
Compiler: /usr/bin/clang
Compilation CFLAGS:  -DPROGRAM='bash' -DCONF_HOSTTYPE='x86_64' -DCONF_OSTYPE='darwin11.4.2' -DCONF_MACHTYPE='x86_64-apple-darwin11.4.2' -DCONF_VENDOR='apple' -DLOCALEDIR='/opt/local/share/locale' -DPACKAGE='bash' -DSHELL -DHAVE_CONFIG_H -DMACOSX   -I.  -I. -I./include -I./lib  -I/opt/local/include -pipe -Os -DSSH_SOURCE_BASHRC -arch x86_64
uname output: Darwin breedzicht.local 11.4.2 Darwin Kernel Version 11.4.2: Thu Aug 23 16:25:48 PDT 2012; root:xnu-1699.32.7~1/RELEASE_X86_64 x86_64
Machine Type: x86_64-apple-darwin11.4.2

Bash Version: 4.3
Patch Level: 42
Release Status: release

Description:
	The substitution ${1+"$@"} should resolve to "$@" if there is at
	least one parameter -- i.e. one word per parameter. This works fine
	if IFS contains any character or is unset. If IFS is empty, it
	instead resolves to the equivalent of "$*", i.e. a single word
	concatenating all the parameters without a separator. IFS should
	not influence the behaviour of "$@" under any circumstances.

	(d)ash variants, AT&T ksh, mksh, zsh, yash all do this correctly.
	bash 2.05b.13 also does this correctly (!). The bug is present in
	bash 3.2.57 and bash 4.3.42.

	(In bash, ${1+"$@"} is redundant, but in some old versions of ksh
	and other shells, if 'set -u' is active, "$@" throws an error if
	there are no parameters, so ${1+"$@"} is used as a workaround. As a
	result, this is often found in cross-platform scripts. These break
	on bash 3 & 4 if fieldsplitting is disabled by emptying IFS.)

Repeat-By:
	$ IFS=''			# bug only occurs on empty IFS
	$ set -- this is a test
	$ printf '|%s|\n' ${1+"$@"}	# generates wrong output
	|thisisatest|
	$ printf '|%s|\n' "$@"		# generates correct output
	|this|
	|is|
	|a|
	|test|

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${1+"$@"} does not generate multiple words if IFS is empty martijn@inlv.org - 2015-12-30 04:40 +0100

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