Combine log files (some gzipped) in Java

Question

I'm wondering if someone can help me accomplish this operation from within Java.

zcat -f -- $(ls -t a_log_file.log*) > combined.log

Where there is a_log_file.log, a_log_file.log.gz.1, a_log_file.log.gz.2 ... I haven't been able to find anything that isn't rather intricate. I suppose, I could also somehow just run this from Java but that feels like a wrong solution.

Answer 1

File logDir = new File("path/to/log/files");
    File[] nonGzippedFiles = logDir.listFiles(new FileFilter() {
        @Override
        public boolean accept(File pathname) {
            return !pathname.getName().contains("gz");
        }
    });
    FileOutputStream combinedLogFiles = new FileOutputStream(new File("path/to/combined.log"));
    for (File nonGzippedFile : nonGzippedFiles) {
        FileInputStream fileInputStream = new FileInputStream(nonGzippedFile);
        int read = 0;
        byte[] buff = new byte[128];
        while ((read = fileInputStream.read(buff)) > 0) {
            combinedLogFiles.write(buff, 0, read);
        }
        fileInputStream.close();
    }
    combinedLogFiles.close();

    // path/to/combined.log now contains all the contents of the log files

You'll have to put in some exception handling. Also this doesn't do the already gzipped logs. I assumed that part