cpoerschke commented on a change in pull request #2284:
URL: https://github.com/apache/lucene-solr/pull/2284#discussion_r568428808
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File path: solr/bin/solr
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@@ -2026,7 +2026,11 @@ if [ "$GC_LOG_OPTS" != "" ]; then
if [ "$JAVA_VENDOR" == "IBM J9" ]; then
gc_log_flag="-Xverbosegclog"
fi
- GC_LOG_OPTS+=("$gc_log_flag:$SOLR_LOGS_DIR/solr_gc.log"
'-XX:+UseGCLogFileRotation' '-XX:NumberOfGCLogFiles=9' '-XX:GCLogFileSize=20M')
+ if [ -z ${JAVA8_GC_LOG_FILE_OPTS+x} ]; then
Review comment:
This variant is consistent with the existing variant at line 2010 but
yes it confused me too when I first read it, looks there's a subtle difference
between "unset" and "set to empty string" behaviour. Illustration:
```
$ unset GC_LOG_OPTS
$ if [ -z ${GC_LOG_OPTS+x} ]; then echo unset; else echo not unset; fi
unset
$ if [ -z ${GC_LOG_OPTS:+x} ]; then echo empty; else echo not empty; fi
empty
$ if [ -z ${GC_LOG_OPTS} ]; then echo empty; else echo not empty; fi
empty
$
$ GC_LOG_OPTS=
$ if [ -z ${GC_LOG_OPTS+x} ]; then echo unset; else echo not unset; fi
not unset
$ if [ -z ${GC_LOG_OPTS:+x} ]; then echo empty; else echo not empty; fi
empty
$ if [ -z ${GC_LOG_OPTS} ]; then echo empty; else echo not empty; fi
empty
$
$ GC_LOG_OPTS=foobar
$ if [ -z ${GC_LOG_OPTS+x} ]; then echo unset; else echo not unset; fi
not unset
$ if [ -z ${GC_LOG_OPTS:+x} ]; then echo empty; else echo not empty; fi
not empty
$ if [ -z ${GC_LOG_OPTS} ]; then echo empty; else echo not empty; fi
not empty
```
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