Cédric Couralet wrote:
...
One question, though, in the tomcat doc (for 6.0.x) for the
JMXRemoteListener, the configuration is :
-Dcom.sun.management.jmxremote.password.file=$CATALINA_BASE/conf/jmxremote.password
-Dcom.sun.management.jmxremote.access.file=$CATALINA_BASE/conf/jmxremote.access
while mine is
-Dcom.sun.management.jmxremote.password.file=${CATALINA_BASE}/conf/jmxremote.password
(notice the {} ).
is it my mistake?
No, it is not a mistake. The above are lines extracted from a shell script, I
presume.
In this particular case, $CATALINA_BASE and ${CATALINA_BASE} are equivalent.
The {} form helps to clarify things for the shell when the character which *follows* the
name of the variable, could be considered by the shell as part of the variable name.
For example in :
echo "something" > $my_file_conf
it is not clear whether the name of the variable is "my" or "my_file" or
"my_file_conf".
(or anything in-between), and by default the shell will use the longer
possibility.
Writing this as
echo "something" > ${my_file}_conf
leaves only one possible interpretation.
In "$CATALINA_BASE/conf/jmxremote.password" there is really no ambiguity (because "/"
cannot be part of a variable name), but the form
"${CATALINA_BASE}/conf/jmxremote.password" is anyway clearer and less prone to oversights.
(But it is slightly more work to type, and as programmers are a notoriously lazy and
hubristic bunch, they rarely go through the trouble).
I suppose that - just to kid Christopher - I could on like this, talking about
interpolation and stuff, but I'll leave it at that because it's already late here.
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