如何从 Java 调用 Linux shell 命令
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How to invoke a Linux shell command from Java
提问by Narek
I am trying to execute some Linux commands from Java using redirection (>&) and pipes (|). How can Java invoke cshor bashcommands?
我正在尝试使用重定向 (>&) 和管道 (|) 从 Java 执行一些 Linux 命令。Java 如何调用csh或bash命令？
I tried to use this:
我试着用这个：
Process p = Runtime.getRuntime().exec("shell command");
But it's not compatible with redirections or pipes.
但它与重定向或管道不兼容。
采纳答案by KitsuneYMG
exec does not execute a command in your shell
exec 不会在你的 shell 中执行命令
try
尝试
Process p = Runtime.getRuntime().exec(new String[]{"csh","-c","cat /home/narek/pk.txt"});
instead.
反而。
EDIT:: I don't have csh on my system so I used bash instead. The following worked for me
编辑:: 我的系统上没有 csh，所以我改用了 bash。以下对我有用
Process p = Runtime.getRuntime().exec(new String[]{"bash","-c","ls /home/XXX"});
回答by Tim
Use ProcessBuilder to separate commands and arguments instead of spaces. This should work regardless of shell used:
使用 ProcessBuilder 来分隔命令和参数而不是空格。无论使用何种外壳，这都应该有效：
import java.io.BufferedReader;
import java.io.File;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.ArrayList;
import java.util.List;
public class Test {
public static void main(final String[] args) throws IOException, InterruptedException {
//Build command
List<String> commands = new ArrayList<String>();
commands.add("/bin/cat");
//Add arguments
commands.add("/home/narek/pk.txt");
System.out.println(commands);
//Run macro on target
ProcessBuilder pb = new ProcessBuilder(commands);
pb.directory(new File("/home/narek"));
pb.redirectErrorStream(true);
Process process = pb.start();
//Read output
StringBuilder out = new StringBuilder();
BufferedReader br = new BufferedReader(new InputStreamReader(process.getInputStream()));
String line = null, previous = null;
while ((line = br.readLine()) != null)
if (!line.equals(previous)) {
previous = line;
out.append(line).append('\n');
System.out.println(line);
}
//Check result
if (process.waitFor() == 0) {
System.out.println("Success!");
System.exit(0);
}
//Abnormal termination: Log command parameters and output and throw ExecutionException
System.err.println(commands);
System.err.println(out.toString());
System.exit(1);
}
}
回答by Evgeni Sergeev
Building on @Tim's example to make a self-contained method:
以@Tim 的示例为基础制作一个自包含的方法：
import java.io.BufferedReader;
import java.io.File;
import java.io.InputStreamReader;
import java.util.ArrayList;
public class Shell {
/** Returns null if it failed for some reason.
*/
public static ArrayList<String> command(final String cmdline,
final String directory) {
try {
Process process =
new ProcessBuilder(new String[] {"bash", "-c", cmdline})
.redirectErrorStream(true)
.directory(new File(directory))
.start();
ArrayList<String> output = new ArrayList<String>();
BufferedReader br = new BufferedReader(
new InputStreamReader(process.getInputStream()));
String line = null;
while ( (line = br.readLine()) != null )
output.add(line);
//There should really be a timeout here.
if (0 != process.waitFor())
return null;
return output;
} catch (Exception e) {
//Warning: doing this is no good in high quality applications.
//Instead, present appropriate error messages to the user.
//But it's perfectly fine for prototyping.
return null;
}
}
public static void main(String[] args) {
test("which bash");
test("find . -type f -printf '%T@\\t%p\\n' "
+ "| sort -n | cut -f 2- | "
+ "sed -e 's/ /\\\\ /g' | xargs ls -halt");
}
static void test(String cmdline) {
ArrayList<String> output = command(cmdline, ".");
if (null == output)
System.out.println("\n\n\t\tCOMMAND FAILED: " + cmdline);
else
for (String line : output)
System.out.println(line);
}
}
(The test example is a command that lists all files in a directory and its subdirectories, recursively, in chronological order.)
（测试示例是一个命令，它按时间顺序递归地列出目录及其子目录中的所有文件。）
By the way, if somebody can tell me why I need four and eight backslashes there, instead of two and four, I can learn something. There is one more level of unescaping happening than what I am counting.
顺便说一句，如果有人能告诉我为什么我需要四个和八个反斜杠，而不是两个和四个，我可以学到一些东西。比我所计算的还要多一层无法逃避的事情发生。
Edit: Just tried this same code on Linux, and there it turns out that I need half as many backslashes in the test command! (That is: the expected number of two and four.) Now it's no longer just weird, it's a portability problem.
编辑：刚刚在 Linux 上尝试了相同的代码，结果我在测试命令中需要一半的反斜杠！（即：预期的 2 和 4 数量。）现在它不再只是奇怪，而是一个可移植性问题。
