Package: dash
Version: 0.5.3-3
Bug first reported against Ubuntu at
https://bugs.launchpad.net/ubuntu/+source/dash/+bug/105634
by Paul Smith
The description and some comments from that bug report follow.
-----
This operation fails on Ubuntu:
$ /bin/sh -c 'if false; then d="${foo/bar}"; fi'
/bin/sh: Syntax error: Bad substitution
When used with other POSIX shells it succeeds. While semantically the
variable reference ${foo/bar} is not valid, this is not a syntax error
according to POSIX, and since the variable assignment expression is
never invoked (because it's within an "if false") it should not be seen
as an error.
I ran into this because after restarting my system I could no longer log
in. It turns out that the problem was (a) I had edited .gnomerc to
source my .bashrc file so that my environment would be set properly, and
(b) I had added some new code to my .bashrc WITHIN A CHECK FOR BASH!
that used bash's ${var/match/sub} feature. Even though this code was
within a "case $BASH_VERSION; in *[0-9]*) ... esac (so dash would never
execute it since that variable is not set), it still caused dash to
throw up.
-----
FYI, some relevant details from POSIX:
Section 2.3, Token Recognition:
5. If the current character is an unquoted '$' or '`', the shell shall
identify the start of any candidates for parameter expansion ( Parameter
Expansion), command substitution ( Command Substitution), or arithmetic
expansion ( Arithmetic Expansion) from their introductory unquoted
character sequences: '$' or "${", "$(" or '`', and "$((", respectively.
The shell shall read sufficient input to determine the end of the unit
to be expanded (as explained in the cited sections).
Section 2.6.2, Parameter Expansion:
The format for parameter expansion is as follows:
${expression}
where expression consists of all characters until the matching '}'. Any
'}' escaped by a backslash or within a quoted string, and characters in
embedded arithmetic expansions, command substitutions, and variable
expansions, shall not be examined in determining the matching '}'.
[...]
The parameter name or symbol can be enclosed in braces, which are
optional except for positional parameters with more than one digit or
when parameter is followed by a character that could be interpreted as
part of the name. The matching closing brace shall be determined by
counting brace levels, skipping over enclosed quoted strings, and
command substitutions.
---
In addition to bash I've checked Solaris /bin/sh and ksh and they don't
report an error.
-----
Micah Cowan:
The applicable portion of POSIX is in XCU 2.10.1:
"The WORD tokens shall have the word expansion rules applied to them
immediately before the associated command is executed, not at the time
the command is parsed."
This seems fairly clear to me.
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