com.sshtools.server.vsession.commands.fs.Follow Maven / Gradle / Ivy

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Support for a virtual sessions, custom command execution etc.

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package com.sshtools.server.vsession.commands.fs;

/*-
 * #%L
 * Virtual Sessions
 * %%
 * Copyright (C) 2002 - 2024 JADAPTIVE Limited
 * %%
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License as
 * published by the Free Software Foundation, either version 3 of the
 * License, or (at your option) any later version.
 * 
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Lesser Public License for more details.
 * 
 * You should have received a copy of the GNU General Lesser Public
 * License along with this program.  If not, see
 * .
 * #L%
 */

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;

import com.sshtools.common.files.AbstractFile;
import com.sshtools.common.permissions.PermissionDeniedException;
import com.sshtools.server.vsession.ShellCommand;
import com.sshtools.server.vsession.VirtualConsole;

public class Follow extends ShellCommand {
	public Follow() {
		super("follow", ShellCommand.SUBSYSTEM_FILESYSTEM, "follow ", "Monitor a file");
		setBuiltIn(false);
	}

	public void run(String[] args, VirtualConsole process)
			throws IOException, PermissionDeniedException {

		if (args.length != 2)
			throw new IOException("A single argument is required");
		try {
			AbstractFile obj = process.getCurrentDirectory().resolveFile(
					args[1]);
			long _filePointer = 0;
			while (true) {
				Thread.sleep(2000);
				long len = obj.getAttributes().size().longValue();
				if (len < _filePointer) {
					process.println(
									"--- TRUNCATED ---   File was reset. Restarting following from start of file.");
					_filePointer = len;
				} else if (len > _filePointer) {
					InputStream in = obj.getInputStream();
					in.skip(_filePointer);
					try(BufferedReader r = new BufferedReader(new InputStreamReader(in))) {
						String line = null;
						while ((line = r.readLine()) != null) {
							process.println(line);
						}
						_filePointer = len;
					} finally {
						in.close();
					}
				}
			}
		} catch (Exception e) {
			process.println("--- ERROR ---   Fatal error following file, following stopped.");
		}
	}
}