how does apache commons-cli parses \\t character

Question

I need to pass tab as an argument in commons-cli. When I give the argument as "\\t", the command line parser parses it as "\t" character itself but not TAB ( ) white space. How can I achieve this?

Edit :

As suggested by @centic, updating the question with how am I calling the application. I am calling using command line in Unix where a backslash is detected as an escape character.

More precisely, I am using it while submitting hadoop streaming jobs, if this helps. For eg :

hadoop jar $HADOOP_HOME/share/hadoop/tools/lib/hadoop-streaming-2.4.0.jar -D stream.map.output.field.separator="\t" -file mapper.py -mapper mapper.py -file reducer.py -reducer reducer.py -input /in -output /out

Apache Hadoop uses Apache Commons-cli as command line utility. So I am assuming "\\t" resolves to "\t" and passed as an option. But when I print it by debugging hadoop source code, instead of a TAB white space character, it prints as a "\t" (string literal) itself.

Answer 1

As you are trying to provide this when invoking the application in the shell, this is actually related to how the shell handles such special characters, not commons-cli or Java.

The bash shell (which is the default shell on most unix/linux versions nowadays) has the special syntax $'\t' for this, see this section in the manual.

So your call would be something like

HADOOP_HOME/share/hadoop/tools/lib/hadoop-streaming-2.4.0.jar -D 
stream.map.output.field.separator=$'\t' -file mapper.py -mapper 
mapper.py -file reducer.py -reducer reducer.py -input /in -output /out