我没有发送一个命令数组，“hello world”到exec（）正确吗？
正确的输出，你好世界：
thufir@mordor:~$ thufir@mordor:~$ java -jar NetBeansProjects/HelloExec/dist/HelloExec.jar Apr 05, 2016 7:11:23 AM net.bounceme.mordor.telnet.Main run INFO: starting.. Apr 05, 2016 7:11:23 AM net.bounceme.mordor.telnet.Telnet <init> INFO: connecting.. Apr 05, 2016 7:11:23 AM net.bounceme.mordor.telnet.Telnet connect INFO: connect.. Apr 05, 2016 7:11:23 AM net.bounceme.mordor.telnet.Telnet connect INFO: [echo hello 1, echo hello 2, echo hello 3] Apr 05, 2016 7:11:24 AM net.bounceme.mordor.telnet.Telnet connect INFO: did process.. Apr 05, 2016 7:11:24 AM net.bounceme.mordor.telnet.Telnet connect INFO: trying.. hello 1 Apr 05, 2016 7:11:24 AM net.bounceme.mordor.telnet.Telnet read SEVERE: exiting.. 0 thufir@mordor:~$ 码：
package net.bounceme.mordor.telnet; import java.io.BufferedReader; import java.io.IOException; import java.io.InputStreamReader; import java.util.ArrayList; import java.util.List; import java.util.Properties; import java.util.logging.Level; import java.util.logging.Logger; import static java.lang.System.out; public class Telnet { private final static Logger LOG = Logger.getLogger(Telnet.class.getName()); public Telnet() { LOG.info("connecting.."); } private List<String> getCommand() { List<String> commands = new ArrayList<>(); commands.add("echo hello 1"); commands.add("echo hello 2"); commands.add("echo hello 3"); return commands; } private void read(Process process) throws IOException, InterruptedException { BufferedReader input = new BufferedReader(new InputStreamReader(process.getInputStream())); String line = null; while ((line = input.readLine()) != null) { out.println(line); } int exitVal = process.waitFor(); LOG.log(Level.SEVERE, "exiting.. {0}", exitVal); } private void connect() { LOG.info("connect.."); Runtime runtime = Runtime.getRuntime(); List<String> cmds = getCommand(); String[] cmdArray = cmds.toArray(new String[cmds.size()]); String command = cmdArray[0]; LOG.info(cmds.toString()); Process process = null; try { process = runtime.exec(command); } catch (IOException ex) { LOG.severe("process wrong"); Logger.getLogger(Telnet.class.getName()).log(Level.SEVERE, null, ex); } LOG.info("did process.."); LOG.info("trying.."); try { read(process); } catch (IOException | InterruptedException ex) { LOG.severe("read wrong"); Logger.getLogger(Telnet.class.getName()).log(Level.SEVERE, null, ex); } } public void tryConnect() { connect(); } }
崩溃：
thufir@mordor:~$ thufir@mordor:~$ java -jar NetBeansProjects/HelloExec/dist/HelloExec.jar Apr 05, 2016 7:12:32 AM net.bounceme.mordor.telnet.Main run INFO: starting.. Apr 05, 2016 7:12:32 AM net.bounceme.mordor.telnet.Telnet <init> INFO: connecting.. Apr 05, 2016 7:12:32 AM net.bounceme.mordor.telnet.Telnet connect INFO: connect.. Apr 05, 2016 7:12:32 AM net.bounceme.mordor.telnet.Telnet connect INFO: [echo hello 1, echo hello 2, echo hello 3] Apr 05, 2016 7:12:32 AM net.bounceme.mordor.telnet.Telnet connect SEVERE: process wrong Apr 05, 2016 7:12:32 AM net.bounceme.mordor.telnet.Telnet connect SEVERE: null java.io.IOException: Cannot run program "echo hello 1": error=2, No such file or directory at java.lang.ProcessBuilder.start(ProcessBuilder.java:1048) at java.lang.Runtime.exec(Runtime.java:620) at java.lang.Runtime.exec(Runtime.java:485) at net.bounceme.mordor.telnet.Telnet.connect(Telnet.java:48) at net.bounceme.mordor.telnet.Telnet.tryConnect(Telnet.java:66) at net.bounceme.mordor.telnet.Main.run(Main.java:17) at net.bounceme.mordor.telnet.Main.main(Main.java:11) Caused by: java.io.IOException: error=2, No such file or directory at java.lang.UNIXProcess.forkAndExec(Native Method) at java.lang.UNIXProcess.<init>(UNIXProcess.java:248) at java.lang.ProcessImpl.start(ProcessImpl.java:134) at java.lang.ProcessBuilder.start(ProcessBuilder.java:1029) ... 6 more Apr 05, 2016 7:12:32 AM net.bounceme.mordor.telnet.Telnet connect INFO: did process.. Apr 05, 2016 7:12:32 AM net.bounceme.mordor.telnet.Telnet connect INFO: trying.. Exception in thread "main" java.lang.NullPointerException at net.bounceme.mordor.telnet.Telnet.read(Telnet.java:30) at net.bounceme.mordor.telnet.Telnet.connect(Telnet.java:57) at net.bounceme.mordor.telnet.Telnet.tryConnect(Telnet.java:66) at net.bounceme.mordor.telnet.Main.run(Main.java:17) at net.bounceme.mordor.telnet.Main.main(Main.java:11) thufir@mordor:~$
当试图使用cmdArray ：
process = runtime.exec(cmdArray);
推理：
…这是因为当exec被赋予一个string时，它首先parsing它（以我们不喜欢的方式）。 相比之下，当exec被赋予一个string数组时，它只是将它传递给操作系统而不parsing它。
https://stackoverflow.com/a/19383655/262852