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// Copyright 2014 Google Inc. All rights reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package com.google.devtools.build.lib.shell;
import java.util.logging.Logger;
/**
* <p>Represents an OS shell, such as "cmd" on Windows or "sh" on Unix-like
* platforms. Currently, Linux and Windows XP are supported.</p>
*
* <p>This class encapsulates shell-specific logic, like how to
* create a command line that uses the shell to invoke another command.
*/
public abstract class Shell {
private static final Logger log =
Logger.getLogger("com.google.devtools.build.lib.shell.Shell");
private static final Shell platformShell;
static {
final String osName = System.getProperty("os.name");
if ("Linux".equals(osName)) {
platformShell = new SHShell();
} else if ("Windows XP".equals(osName)) {
platformShell = new WindowsCMDShell();
} else {
log.severe("OS not supported; will not be able to execute commands");
platformShell = null;
}
log.config("Loaded shell support '" + platformShell +
"' for OS '" + osName + "'");
}
private Shell() {
// do nothing
}
/**
* @return {@link Shell} subclass appropriate for the current platform
* @throws UnsupportedOperationException if no such subclass exists
*/
public static Shell getPlatformShell() {
if (platformShell == null) {
throw new UnsupportedOperationException("OS is not supported");
}
return platformShell;
}
/**
* Creates a command line suitable for execution by
* {@link Runtime#exec(String[])} from the given command string,
* a command line which uses a shell appropriate for a particular
* platform to execute the command (e.g. "/bin/sh" on Linux).
*
* @param command command for which to create a command line
* @return String[] suitable for execution by
* {@link Runtime#exec(String[])}
*/
public abstract String[] shellify(final String command);
/**
* Represents the <code>sh</code> shell commonly found on Unix-like
* operating systems, including Linux.
*/
private static final class SHShell extends Shell {
/**
* <p>Returns a command line which uses <code>cmd</code> to execute
* the {@link Command}. Given the command <code>foo bar baz</code>,
* for example, this will return a String array corresponding
* to the command line:</p>
*
* <p><code>/bin/sh -c "foo bar baz"</code></p>
*
* <p>That is, it always returns a 3-element array.</p>
*
* @param command command for which to create a command line
* @return String[] suitable for execution by
* {@link Runtime#exec(String[])}
*/
@Override public String[] shellify(final String command) {
if (command == null || command.length() == 0) {
throw new IllegalArgumentException("command is null or empty");
}
return new String[] { "/bin/sh", "-c", command };
}
}
/**
* Represents the Windows command shell <code>cmd</code>.
*/
private static final class WindowsCMDShell extends Shell {
/**
* <p>Returns a command line which uses <code>cmd</code> to execute
* the {@link Command}. Given the command <code>foo bar baz</code>,
* for example, this will return a String array corresponding
* to the command line:</p>
*
* <p><code>cmd /S /C "foo bar baz"</code></p>
*
* <p>That is, it always returns a 4-element array.</p>
*
* @param command command for which to create a command line
* @return String[] suitable for execution by
* {@link Runtime#exec(String[])}
*/
@Override public String[] shellify(final String command) {
if (command == null || command.length() == 0) {
throw new IllegalArgumentException("command is null or empty");
}
return new String[] { "cmd", "/S", "/C", command };
}
}
}
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