问题描述
我试图在 linux 环境中获取管道命令的输出,但到目前为止没有运气。
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);
}
}
当我在没有指定脚本执行器 (/bin/bash -c) 的情况下尝试时:top: unkNown option '|'
解决方法
shell 命令应该是在 -c
之后传递的单个参数。被调用的 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}'");
为了获得稳健性加分,将变量作为单独的参数传递,而不是将它们注入到字符串中(就像您在 SQL 中使用预准备语句的方式):
ProcessBuilder pb = new ProcessBuilder("/bin/sh","top -b -n 2 -d 0.2 -p \"$1\" | tail -1 | awk '{print $6}'","_",String.valueOf(pid));
当 pid
是整数时没有区别,但如果它是任意字符串,这会提高安全性和健壮性。