Java中的awk命令 [英] awk commands in Java

问题描述

我想在Java中使用awk命令行.为此，我有以下代码(我在教程中看到了此代码):

I want to use awk command line in Java. For that, I have this code (I saw this code in a tutorial):

Map map = new HashMap();
map.put("file", new File(fileDirectory)); 

CommandLine cmdLine = new CommandLine("awk"); 
cmdLine.addArgument("{print $1}", false); 
cmdLine.addArgument("${file}"); 
cmdLine.setSubstitutionMap(map);
System.out.println(cmdLine.toString()); 

DefaultExecuteResultHandler resultHandler = new   DefaultExecuteResultHandler();  
ExecuteWatchdog watchdog = new ExecuteWatchdog(10000); 
DefaultExecutor executor = new DefaultExecutor(); 
executor.setWatchdog(watchdog); 
executor.execute(cmdLine, resultHandler); 

resultHandler.waitFor(); 

在此示例中，我的代码显示了文件的第一列.

In this example my code prints the first column of the file.

10
10
10
10
10
10
10
10
10
10
10
10
10
10
10

我想将输出打印到文件中，但是我无法弄清楚.

I want to print the output in a file but I can't figure it out.

推荐答案

通常，要在Java中以编程方式运行awk命令，可以使用

In general to run awk command programmatically in Java you can use Jawk. I was required to build it myself but not a big deal. I have tested with version 1.03 to programmatically call the awk command like below for my use-case.

            String[] awkArgs= { "-f", awkProgramPath };
            // Create a stream to hold the output
            ByteArrayOutputStream baos = new ByteArrayOutputStream();
            PrintStream ps = new PrintStream(baos);
            // Tell Java to use your byte arrya output stream temporarily
            System.setOut(ps);

            AwkParameters parameters = new AwkParameters(Main.class, null);
            AwkSettings settings = parameters.parseCommandLineArguments(awkArgs);

            //Instead of passing file as argument setting the file content as input. 
            //This is done to adapt the line delimiters in file content to the specific OS. Otherwise Jawk fails in splitting the lines.
            //If it is not required, this step cab be skipped and the input file path can be passed as additional argument
            String inputFileContent = new String(Files.readAllBytes(inputFile.toPath())); 
            //Adapting line delimiter.
            inputFileContent = inputFileContent.replaceAll("[\r]?\n", System.getProperty("line.separator"));
            settings.setInput(new ByteArrayInputStream(inputFileContent.getBytes()));

            //Invoking the awk command
            Awk awk = new Awk();
            awk.invoke(settings);
            //Set the old print stream back. May be you can do it in try..finally block to be failsafe.
            System.setOut(sysout);
            //Get the output from byte array output stream
            String output = baos.toString();

您可能需要在sawk.jar内部所需的类路径中添加slf4j.jar.

You may be required to add slf4j.jar in classpath which is required by the jawk.jar internally.

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