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https://issues.apache.org/jira/browse/HADOOP-7494?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13081030#comment-13081030
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Daryn Sharp commented on HADOOP-7494:
-------------------------------------
bq. And i think the pattern match is necessary because the error msg displayed
by parseLong() is strange if bytes specified like this -c+-10 or -c+10+.
I'm not sure what you mean... {{parseLong()}} seems to always throw
{{java.lang.NumberFormatException: For input string: "something"}} for bad
input. Wouldn't something like this do what you want?
{code}
try {
startingOffset = Long.parseLong(arg);
} catch (NumberFormatException)
throw new NumberFormatException(arg + ": invalid number of bytes"); // note
no trailing "." too
}
{code}
Other generally small issues:
# I generally like to see items in alphabetical order, in this case the usage
options.
# I'd suggest changing {{processOffset()}} to {{preprocessOptions()}} and let
it locate the {{-c}}.
# Code removes the {{-c}} when a number is glued on. May as well remove the
{{-c}} too when it has an argument.
# I think you can remove the pattern compile and use above snippet.
# Should set {{showLastBytes}} in both cases in the event the object is reused.
# {{arg.replace("+", "0")}} isn't right. It's going to replace all occurrences
of + with 0. It also makes a lone + be a valid argument of 0. Should use
{{arg.substring(1)}} to strip the leading +.
# You're right about subtracting 1! The fact that both 0 & 1 are 0 offset is
odd.
For the last few points, perhaps something like this might work:
{code}
if (arg.startsWith("+")) {
arg = arg.substr(arg,1);
isNegativeOffset = false; // you can leave this showLastBytes if you want
} else {
if (!arg.startsWith("-")) {
arg = "-".concat(arg);
}
isNegativeOffset = true;
}
// parseLong() with exception cited earlier
if (startingOffset != 0) {
startingOffset += isNegativeOffset ? 1 : -1;
}
{code}
I hope this helps!
> Add -c option for FSshell -tail
> -------------------------------
>
> Key: HADOOP-7494
> URL: https://issues.apache.org/jira/browse/HADOOP-7494
> Project: Hadoop Common
> Issue Type: Improvement
> Components: fs
> Affects Versions: 0.23.0
> Reporter: XieXianshan
> Assignee: XieXianshan
> Priority: Trivial
> Fix For: 0.23.0
>
> Attachments: HADOOP-7494-v0.2.patch, HADOOP-7494.patch
>
>
> Add the "-c" option for FSshell -tail to allow users to specify the output
> bytes(currently,it's -1024 by default).
> For instance:
> $ hdfs dfs -tail -c -10 /user/hadoop/xiexs
> or
> $ hdfs dfs -tail -c+10 /user/hadoop/xiexs
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