Bash string substitution bug (?)
Configuration Information [Automatically generated, do not change]:
Machine: x86_64
OS: linux-gnu
Compiler: x86_64-redhat-linux-gcc
Compilation CFLAGS: -DPROGRAM='bash' -DCONF_HOSTTYPE='x86_64'
-DCONF_OSTYPE='linux-gnu' -DCONF_MACHTYPE='x86_64-redhat-linux-gnu'
-DCONF_VENDOR='redhat' -DLOCALEDIR='/usr/share/locale' -DPACKAGE='bash'
-DSHELL -DHAVE_CONFIG_H -I. -I. -I./include -I./lib -O2 -g -pipe -m64
uname output: Linux acl201.unx.sas.com 2.6.9-42.ELsmp #1 SMP Wed Jul 12
23:32:02 EDT 2006 x86_64 x86_64 x86_64 GNU/Linux
Machine Type: x86_64-redhat-linux-gnu
Bash Version: 3.0
Patch Level: 15
Release Status: release
Description:
unexpected bad substitution:
enter the following simple list:
prompt: CLUSTER='1 2'; echo ${CLUSTER/${HOSTNAME%%.*}}
output: 1 2
the idea of the above line is to remove short HOSTNAME (without the
trailing domain)
from the CLUSTER - works fine (CLUSTER was assigned a dummy
value - irrelevant)
however the same operation with slash results in a bad substitution
error.
the substitution appears to be a valid one.
prompt: CLUSTER='1 2'; echo ${CLUSTER/${HOSTNAME/.*}}
output: -bash: ${HOSTNAME: bad substitution
Repeat-By:
Fix:
Re: Bash string substitution bug (?)
Dmitry V Golovashkin schrieb:
Description:
unexpected bad substitution:
enter the following simple list:
prompt: CLUSTER='1 2'; echo ${CLUSTER/${HOSTNAME%%.*}}
output: 1 2
the idea of the above line is to remove short HOSTNAME (without the
trailing domain)
from the CLUSTER - works fine (CLUSTER was assigned a dummy
value - irrelevant)
however the same operation with slash results in a bad substitution
error.
the substitution appears to be a valid one.
prompt: CLUSTER='1 2'; echo ${CLUSTER/${HOSTNAME/.*}}
output: -bash: ${HOSTNAME: bad substitution
Apparently bash interprets this as ${parameter/pattern/string}
where pattern = ${HOSTNAME. Looks like a bug; it works in ksh.
As a workaround, you could use:
H=${HOSTNAME/.*}
echo ${CLUSTER/$H}
Regards,
Bernd
--
Bernd Eggink
[EMAIL PROTECTED]
http://sudrala.de
Re: Bash string substitution bug (?)
Bernd Eggink wrote:
prompt: CLUSTER='1 2'; echo ${CLUSTER/${HOSTNAME/.*}}
output: -bash: ${HOSTNAME: bad substitution
Apparently bash interprets this as ${parameter/pattern/string}
where pattern = ${HOSTNAME. Looks like a bug; it works in ksh.
That is, in fact, what is happening. I'm not sure you can call it
a bug, though -- bash is behaving exactly as documented. The fact
that Korn chose to implement it a certain way in ksh and not document
the implementation doesn't help compatibility, but the public
specification of the feature is the same between both shells.
Chet
--
``The lyf so short, the craft so long to lerne.'' - Chaucer
Live Strong. No day but today.
Chet Ramey, ITS, CWRU[EMAIL PROTECTED]http://cnswww.cns.cwru.edu/~chet/
Re: Bash string substitution bug (?)
Chet Ramey schrieb:
Bernd Eggink wrote:
prompt: CLUSTER='1 2'; echo ${CLUSTER/${HOSTNAME/.*}}
output: -bash: ${HOSTNAME: bad substitution
Apparently bash interprets this as ${parameter/pattern/string}
where pattern = ${HOSTNAME. Looks like a bug; it works in ksh.
That is, in fact, what is happening. I'm not sure you can call it
a bug, though -- bash is behaving exactly as documented.
Where exactly is that documented? The only statement I can find in the
documentation referring to this problem is:
When braces are used, the matching ending brace is the first `}' not
escaped by a backslash or within a quoted string, and not
within an embedded arithmetic expansion, command substitution, or
parameter expansion.
I may be wrong, but to me this means that the first opening brace
matches the last closing one, and that the token ${HOSTNAME/.*} is a
correct parameter expansion.
Bernd
--
Bernd Eggink
[EMAIL PROTECTED]
http://sudrala.de
Re: Bash string substitution bug (?)
either
VALUE=host1.blah.com
echo ${VALUE//.*}
or
echo ${VALUE/.*}
is accepted by Bash and works exactly as I would expect it - meaning
it correctly produces host1 - removes the dot (dot is just a character
- we are not
in the regular expression world) - so the dot and the trailing domain
name are removed. Bash works fine in both above cases, produces expected
output;
${VALUE/.*} naturally seems to be a valid parameter expansion.
Please try once more:
CLUSTER='host5 host1 host2';
VALUE=host1.blah.com;
echo ${CLUSTER//${VALUE%%.*}}
again works perfectly: Outputs 'host5 host2' just as i would expect it.
${VALUE%%.*} similarly to ${VALUE//.*} just removes the first
dot-and-the-trailing domain name.
it is logical to assume and the manual supports it that
echo ${CLUSTER//${VALUE%%.*}}
is a valid parameter expansion. Again - it works fine.
Therefore it seems to be inconsistent that the nearly identical
expansion
echo ${CLUSTER//${VALUE/.*}}
is throwing bad substitution exception.
To sum things up, consider these two lines (without the dot):
echo ${CLUSTER//${VALUE%%*}}
echo ${CLUSTER//${VALUE//*}}
the first works great. the second results in bash: ${VALUE: bad
substitution
It really does seem remarkably inconsistent: We have parameter expansion
within parameter expansion, one works fine, nearly identical another one
throws an exception... Seems a bug to me.
Thanks!
dm
PS echo ${CLUSTER//${VALUE##.*}}
also works superb - in this case ${VALUE##.*} is empty - because VALUE
does not start with a dot.
Bash works great here too. It is only when // is used - Bash
misbehaves...
Bernd Eggink wrote:
Chet Ramey schrieb:
Bernd Eggink wrote:
prompt: CLUSTER='1 2'; echo ${CLUSTER/${HOSTNAME/.*}}
output: -bash: ${HOSTNAME: bad substitution
Apparently bash interprets this as ${parameter/pattern/string}
where pattern = ${HOSTNAME. Looks like a bug; it works in ksh.
That is, in fact, what is happening. I'm not sure you can call it
a bug, though -- bash is behaving exactly as documented.
Where exactly is that documented? The only statement I can find in the
documentation referring to this problem is:
When braces are used, the matching ending brace is the first `}' not
escaped by a backslash or within a quoted string, and not
within an embedded arithmetic expansion, command substitution, or
parameter expansion.
I may be wrong, but to me this means that the first opening brace
matches the last closing one, and that the token ${HOSTNAME/.*} is a
correct parameter expansion.
Bernd
--
Bernd Eggink
[EMAIL PROTECTED]
http://sudrala.de
