Public bug reported:
The man page says, under "Word Expansions", that output from Command
Substitution will be later split into fields (unless IFS is null).
Therefore the statement
foo=$(echo xxx bar=yyy)
should expand to
foo=xxx bar=yyy
and when executed, set two variables foo and bar.
However dash does not do this. Instead, the Command Substitution output
is not split, and the result is the same as
foo="xxx bar=yyy"
which sets a single variable.
HOWEVER, inside a function, dash *does* split the result of Command
Substitution if it is part of a 'local' variable declaration.
This seems inconsistent: One or the other case must be a bug.
Comment: Despite what the man says, splitting Command Substitution
results is probably not desirable and would be incompatible with bash
(which AFAIK never splits Command Subst output). I can't say what POSIX
mandates about this.
#!/usr/bin/env dash
func() {
echo "IFS='$IFS'"
gvar=$(echo "11 y=22")
local lvar=$(echo "33 z=44")
echo "gvar=$gvar"
echo "y=$y"
echo "lvar=$lvar"
echo "z=$z"
}
func
# RESULTS:
#
# IFS='
# '
# gvar=11 y=22
# y=
# lvar=33
# z=44
ProblemType: Bug
DistroRelease: Ubuntu 16.04
Package: dash 0.5.8-2.1ubuntu2
ProcVersionSignature: Ubuntu 4.4.0-66.87-generic 4.4.44
Uname: Linux 4.4.0-66-generic x86_64
NonfreeKernelModules: nvidia_uvm nvidia_drm nvidia_modeset nvidia
ApportVersion: 2.20.1-0ubuntu2.5
Architecture: amd64
CurrentDesktop: Unity
Date: Fri Mar 10 16:33:07 2017
InstallationDate: Installed on 2017-01-19 (50 days ago)
InstallationMedia: Ubuntu 16.04.1 LTS "Xenial Xerus" - Release amd64 (20160719)
SourcePackage: dash
UpgradeStatus: No upgrade log present (probably fresh install)
** Affects: dash (Ubuntu)
Importance: Undecided
Status: New
** Tags: amd64 apport-bug xenial
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https://bugs.launchpad.net/bugs/1671977
Title:
Inconsistent splitting of results of $(Command Substitution)
Status in dash package in Ubuntu:
New
Bug description:
The man page says, under "Word Expansions", that output from Command
Substitution will be later split into fields (unless IFS is null).
Therefore the statement
foo=$(echo xxx bar=yyy)
should expand to
foo=xxx bar=yyy
and when executed, set two variables foo and bar.
However dash does not do this. Instead, the Command Substitution
output is not split, and the result is the same as
foo="xxx bar=yyy"
which sets a single variable.
HOWEVER, inside a function, dash *does* split the result of Command
Substitution if it is part of a 'local' variable declaration.
This seems inconsistent: One or the other case must be a bug.
Comment: Despite what the man says, splitting Command Substitution
results is probably not desirable and would be incompatible with bash
(which AFAIK never splits Command Subst output). I can't say what
POSIX mandates about this.
#!/usr/bin/env dash
func() {
echo "IFS='$IFS'"
gvar=$(echo "11 y=22")
local lvar=$(echo "33 z=44")
echo "gvar=$gvar"
echo "y=$y"
echo "lvar=$lvar"
echo "z=$z"
}
func
# RESULTS:
#
# IFS='
# '
# gvar=11 y=22
# y=
# lvar=33
# z=44
ProblemType: Bug
DistroRelease: Ubuntu 16.04
Package: dash 0.5.8-2.1ubuntu2
ProcVersionSignature: Ubuntu 4.4.0-66.87-generic 4.4.44
Uname: Linux 4.4.0-66-generic x86_64
NonfreeKernelModules: nvidia_uvm nvidia_drm nvidia_modeset nvidia
ApportVersion: 2.20.1-0ubuntu2.5
Architecture: amd64
CurrentDesktop: Unity
Date: Fri Mar 10 16:33:07 2017
InstallationDate: Installed on 2017-01-19 (50 days ago)
InstallationMedia: Ubuntu 16.04.1 LTS "Xenial Xerus" - Release amd64
(20160719)
SourcePackage: dash
UpgradeStatus: No upgrade log present (probably fresh install)
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