在Shell脚本中执行Java程序时使用双引号

Question

I have a shell script that executes a Java program with parameters returned from a different Java program.

java -cp $wekaPath $(java GetFilter $WandFDir) -i $(pwd)/temp/training"$i"_$arffName.arff -o $(pwd)/temp/training_"$i"_$arffName.arff

When echoed, it produces the following string:

java -cp /home/robobenny/Documents/WEKA/weka-3-7-4/weka.jar weka.filters.supervised.attribute.AttributeSelection -E "weka.attributeSelection.InfoGainAttributeEval" -S "weka.attributeSelection.Ranker -T -1.7976931348623157E308 -N 20" -c first -i /home/robobenny/Documents/WEKA/Pipeline/temp/training1_Test.arff -o /home/robobenny/Documents/WEKA/Pipeline/temp/training_1_Test.arff

Which is great, because if I copy the string to the command line, it runs the Java program without incident. The problem arises when I don't echo it and try to execute it from the shell script, and I get the following from the terminal:

<!-- language: lang-none -->
Can't find class called: "weka.attributeSelection.InfoGainAttributeEval"
Filter options:

-S <"Name of search class [search options]">
    Sets search method for subset evaluators.
    eg. -S "weka.attributeSelection.BestFirst -S 8"
-E <"Name of attribute/subset evaluation class [evaluator options]">
    Sets attribute/subset evaluator.
    eg. -E "weka.attributeSelection.CfsSubsetEval -L"

Options specific to evaluator weka.attributeSelection.CfsSubsetEval:

-M
    Treat missing values as a separate value.
-L
    Don't include locally predictive attributes.

Options specific to search weka.attributeSelection.BestFirst:

-P <start set>
    Specify a starting set of attributes.
    Eg. 1,3,5-7.
-D <0 = backward | 1 = forward | 2 = bi-directional>
    Direction of search. (default = 1).
-N <num>
    Number of non-improving nodes to
    consider before terminating search.
-S <num>
    Size of lookup cache for evaluated subsets.
    Expressed as a multiple of the number of
    attributes in the data set. (default = 1)

General options:

-h
    Get help on available options.
    (use -b -h for help on batch mode.)
-i <file>
    The name of the file containing input instances.
    If not supplied then instances will be read from stdin.
-o <file>
    The name of the file output instances will be written to.
    If not supplied then instances will be written to stdout.
-c <class index>
    The number of the attribute to use as the class.
    "first" and "last" are also valid entries.
    If not supplied then no class is assigned.

When I hard code the output of $(java GetFilter $WandFDir) in the shell script:

java -cp $wekaPath weka.filters.supervised.attribute.AttributeSelection -E "weka.attributeSelection.InfoGainAttributeEval" -S "weka.attributeSelection.Ranker -T -1.7976931348623157E308 -N 20" -c first -i $(pwd)/temp/training"$i"_$arffName.arff -o $(pwd)/temp/training_"$i"_$arffName.arff

It also runs without incident. Interestingly though, when echoed, the double quotes disappear.

java -cp /home/robobenny/Documents/WEKA/weka-3-7-4/weka.jar weka.filters.supervised.attribute.AttributeSelection -E weka.attributeSelection.InfoGainAttributeEval -S weka.attributeSelection.Ranker -T -1.7976931348623157E308 -N 20 -c first -i /home/robobenny/Documents/WEKA/Pipeline/temp/training2_Test.arff -o /home/robobenny/Documents/WEKA/Pipeline/temp/training_2_Test.arff

When I leave the double quotes out of the output of $(java GetFilter $WandFDir) I get the following error:

<!-- language: lang-none -->
Illegal options: -T -1.7976931348623157E308 -N 20 
Filter options:

-S <"Name of search class [search options]">
    Sets search method for subset evaluators.
    eg. -S "weka.attributeSelection.BestFirst -S 8"
-E <"Name of attribute/subset evaluation class [evaluator options]">
    Sets attribute/subset evaluator.
    eg. -E "weka.attributeSelection.CfsSubsetEval -L"

Options specific to evaluator weka.attributeSelection.InfoGainAttributeEval:

-M
    treat missing values as a seperate value.
-B
    just binarize numeric attributes instead 
    of properly discretizing them.

Options specific to search weka.attributeSelection.Ranker:

-P <start set>
    Specify a starting set of attributes.
    Eg. 1,3,5-7.
    Any starting attributes specified are
    ignored during the ranking.
-T <threshold>
    Specify a theshold by which attributes
    may be discarded from the ranking.
-N <num to select>
    Specify number of attributes to select

General options:

-h
    Get help on available options.
    (use -b -h for help on batch mode.)
-i <file>
    The name of the file containing input instances.
    If not supplied then instances will be read from stdin.
-o <file>
    The name of the file output instances will be written to.
    If not supplied then instances will be written to stdout.
-c <class index>
    The number of the attribute to use as the class.
    "first" and "last" are also valid entries.
    If not supplied then no class is assigned.

I've looked around, and can't seem to find anything that solves my problem.

Answer 1

It's really a catch at the straw, but did you try something like

var="$(java GetFilter $WandFDir)"
java -cp $wekaPath $var -i $(pwd)/temp/training"$i"_$arffName.arff -o $(pwd)/temp/training_"$i"_$arffName.arff