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https://issues.apache.org/jira/browse/HADOOP-14976?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16219364#comment-16219364
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Arpit Agarwal commented on HADOOP-14976:
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I see, thank you for the clarification.
In this case, the scripts were historically renamed to allow multi-versioning -
during upgrades for example. Perhaps the 3.0 script rewrite makes it easier to
do this differently. I can guess why the variable name detection is done this
way in 3.0 - it allows separating out script-specific logic into the generic
hadoop-functions.sh which is neat.
For now it's just an unexpected side effect that rename breaks the
interpretation of shell variables. My first thought was letting script callers
override HADOOP_SHELL_EXECNAME, so scripts don't initialize it if it's already
set. One situation where that might break things is when one script invokes and
we want HADOOP_SHELL_EXECNAME to reflect the callee script. It looks like that
doesn't happen today though, scripts like hadoop-distcp.sh and
hadoop-streaming.sh don't rewrite HADOOP_SHELL_EXECNAME.
> Allow overriding HADOOP_SHELL_EXECNAME
> --------------------------------------
>
> Key: HADOOP-14976
> URL: https://issues.apache.org/jira/browse/HADOOP-14976
> Project: Hadoop Common
> Issue Type: Improvement
> Reporter: Arpit Agarwal
>
> Some Hadoop shell scripts infer their own name using this bit of shell magic:
> {code}
> 18 MYNAME="${BASH_SOURCE-$0}"
> 19 HADOOP_SHELL_EXECNAME="${MYNAME##*/}"
> {code}
> e.g. see the
> [hdfs|https://github.com/apache/hadoop/blob/trunk/hadoop-hdfs-project/hadoop-hdfs/src/main/bin/hdfs#L18]
> script.
> The inferred shell script name is later passed to _hadoop-functions.sh_ which
> uses it to construct the names of some environment variables. E.g. when
> invoking _hdfs datanode_, the options variable name is inferred as follows:
> {code}
> # HDFS + DATANODE + OPTS -> HDFS_DATANODE_OPTS
> {code}
> This works well if the calling script name is standard {{hdfs}} or {{yarn}}.
> If a distribution renames the script to something like foo.bar, , then the
> variable names will be inferred as {{FOO.BAR_DATANODE_OPTS}}. This is not a
> valid bash variable name.
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