[英]Java Run Command pipe on linux
我试图在 linux 环境中获取管道命令的 output 但到目前为止还没有运气。
ProcessBuilder pb = new ProcessBuilder("/bin/sh", "-c", "top", "-b", "-n", "2", "-d", "0.2", "-p", pid + "", "|", "tail", "-1", "|", "awk", "'{print $6}'");
pb.redirectErrorStream(true);
Process p = pb.start();
p.getOutputStream().close();
try (InputStream is = p.getInputStream()) {
try (BufferedReader br = new BufferedReader(new InputStreamReader(is))) {
String line = br.readLine();
System.out.println(line);
}
}
这输出: top: failed tty get
当我尝试不指定脚本执行程序 (/bin/bash -c): top: unknown option '|'
shell 命令应该是在-c
之后传递的单个参数。 调用的 shell 将负责管道和标记化:
ProcessBuilder pb = new ProcessBuilder("/bin/sh", "-c",
"top -b -n 2 -d 0.2 -p " + pid + " | tail -1 | awk '{print $6}'");
对于健壮性加分,将变量作为单独的 arguments 传递,而不是将它们注入到字符串中(就像您在 SQL 中使用准备好的语句一样):
ProcessBuilder pb = new ProcessBuilder("/bin/sh", "-c",
"top -b -n 2 -d 0.2 -p \"$1\" | tail -1 | awk '{print $6}'", "_", String.valueOf(pid));
当pid
是 integer 时没有区别,但如果它是任意字符串,这将提高安全性和鲁棒性。
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