Java调用Linux命令

Java可以直接调用Linux命令，形式如下：
 Runtime.getRuntime().exec(command)

 举例：运行ls,top命令可以这样：
 Runtime.getRuntime().exec("ls");

 但是这样执行时没有任何输出，原因： 
 调用Runtime.exec方法将产生一个本地的进程,并返回一个Process子类的实例，
（注意：Runtime.getRuntime().exec（command）返回的是一个Process类的实例）,
该实例可用于控制进程或取得进程的相关信息. 由于调用Runtime.exec方法所创建的子进程没有自己的终端或控制台,因此该子进程的标准IO(如stdin,stdou,stderr)都通过Process.getOutputStream(),Process.getInputStream(), Process.getErrorStream()方法重定向给它的父进程了.用户需要用这些stream来向子进程输入数据或获取子进程的输出. 可以采用如下方法：

try
{
 Process process = Runtime.getRuntime().exec ("ls"); 

 InputStreamReader ir=newInputStreamReader(process.getInputStream());
 LineNumberReader input = new LineNumberReader (ir);

 String line;
 while ((line = input.readLine ()) != null){
  System.out.println(line)
}
catch (java.io.IOException e){
 System.err.println ("IOException " + e.getMessage());
}

评论

2 楼 fandayrockworld 2012-01-07  

p.waitFor();

avery_leo 写道

Java代码
public static double[] getMemUsage() throws Exception {  
 
        double[] result = new double[4];  
          
        Process p = rt.exec("free -m");// 调用系统的命令  
          
        BufferedReader in = null;  
        try {  
            in = new BufferedReader(new InputStreamReader(p.getInputStream()));  
            String str = null;  
            String[] strArray = null;  
 
            while ((str = in.readLine()) != null) {  
                 

public static double[] getMemUsage() throws Exception {

double[] result = new double[4];

Process p = rt.exec("free -m");// 调用系统的命令

BufferedReader in = null;
try {
in = new BufferedReader(new InputStreamReader(p.getInputStream()));
String str = null;
String[] strArray = null;

while ((str = in.readLine()) != null) {
Java代码
        int m = 0;  
 
        if (str.indexOf("/") != -1) {// MemUsed  
                                                    strArray = str.split(" ");  
            for (String tmp : strArray) {  
                if (tmp.trim().length() == 0)  
                    continue;  
 
                if (++m == 3) {  
                                                result[1] = Double.parseDouble(tmp);  
 
                }  
            }  
 
        }  
        if (str.indexOf("Mem") != -1) {// MemTotal  
 
            strArray = str.split(" ");  
            for (String tmp : strArray) {  
                if (tmp.trim().length() == 0)  
                    continue;  
 
                if (++m == 2) {  
 
                    result[0] = Double.parseDouble(tmp);  
 
                }  
            }  
 
        }  
    }  
    p.getErrorStream();  
} catch (Exception e) {  
    e.printStackTrace();  
} finally {  
    in.close();  
    p.destroy();  
}  
// System.out.println("Performance Monitoring menUsed:" + result[1]);  
return result;  

int m = 0;

if (str.indexOf("/") != -1) {// MemUsed
strArray = str.split(" ");
for (String tmp : strArray) {
if (tmp.trim().length() == 0)
continue;

if (++m == 3) {
result[1] = Double.parseDouble(tmp);

}
}

}
if (str.indexOf("Mem") != -1) {// MemTotal

strArray = str.split(" ");
for (String tmp : strArray) {
if (tmp.trim().length() == 0)
continue;

if (++m == 2) {

result[0] = Double.parseDouble(tmp);

}
}

}
}
p.getErrorStream();
} catch (Exception e) {
e.printStackTrace();
} finally {
in.close();
p.destroy();
}
// System.out.println("Performance Monitoring menUsed:" + result[1]);
return result;
}


在一个线程（假设1毫秒一次）中，无限循环执行上面的代码：



大概20分钟左右后出现如下异常：



java.io.IOException: Cannot run program "free": java.io.IOException: error=24, Too many open files
        at java.lang.ProcessBuilder.start(ProcessBuilder.java:459)
        at java.lang.Runtime.exec(Runtime.java:593)
        at java.lang.Runtime.exec(Runtime.java:431)
        at java.lang.Runtime.exec(Runtime.java:328)
        at LinuxSystemTool.getMemUsage(LinuxSystemTool.java:98)
        at LinuxSystemTool.exec(LinuxSystemTool.java:67)
        at LinuxSystemTool.run(LinuxSystemTool.java:42)
        at java.lang.Thread.run(Thread.java:619)
Caused by: java.io.IOException: java.io.IOException: error=24, Too many open files
        at java.lang.UNIXProcess.<init>(UNIXProcess.java:148)
        at java.lang.ProcessImpl.start(ProcessImpl.java:65)
        at java.lang.ProcessBuilder.start(ProcessBuilder.java:452)
        ... 7 more



查看网络相关资料，大概了解可能是由于打开的句柄过多造成，也没有找到解决办法，不吝赐教，谢谢

1 楼 avery_leo 2009-01-04  

Java代码
public static double[] getMemUsage() throws Exception {  
 
        double[] result = new double[4];  
          
        Process p = rt.exec("free -m");// 调用系统的命令  
          
        BufferedReader in = null;  
        try {  
            in = new BufferedReader(new InputStreamReader(p.getInputStream()));  
            String str = null;  
            String[] strArray = null;  
 
            while ((str = in.readLine()) != null) {  
                 

public static double[] getMemUsage() throws Exception {

double[] result = new double[4];

Process p = rt.exec("free -m");// 调用系统的命令

BufferedReader in = null;
try {
in = new BufferedReader(new InputStreamReader(p.getInputStream()));
String str = null;
String[] strArray = null;

while ((str = in.readLine()) != null) {
Java代码
        int m = 0;  
 
        if (str.indexOf("/") != -1) {// MemUsed  
                                                    strArray = str.split(" ");  
            for (String tmp : strArray) {  
                if (tmp.trim().length() == 0)  
                    continue;  
 
                if (++m == 3) {  
                                                result[1] = Double.parseDouble(tmp);  
 
                }  
            }  
 
        }  
        if (str.indexOf("Mem") != -1) {// MemTotal  
 
            strArray = str.split(" ");  
            for (String tmp : strArray) {  
                if (tmp.trim().length() == 0)  
                    continue;  
 
                if (++m == 2) {  
 
                    result[0] = Double.parseDouble(tmp);  
 
                }  
            }  
 
        }  
    }  
    p.getErrorStream();  
} catch (Exception e) {  
    e.printStackTrace();  
} finally {  
    in.close();  
    p.destroy();  
}  
// System.out.println("Performance Monitoring menUsed:" + result[1]);  
return result;  

int m = 0;

if (str.indexOf("/") != -1) {// MemUsed
strArray = str.split(" ");
for (String tmp : strArray) {
if (tmp.trim().length() == 0)
continue;

if (++m == 3) {
result[1] = Double.parseDouble(tmp);

}
}

}
if (str.indexOf("Mem") != -1) {// MemTotal

strArray = str.split(" ");
for (String tmp : strArray) {
if (tmp.trim().length() == 0)
continue;

if (++m == 2) {

result[0] = Double.parseDouble(tmp);

}
}

}
}
p.getErrorStream();
} catch (Exception e) {
e.printStackTrace();
} finally {
in.close();
p.destroy();
}
// System.out.println("Performance Monitoring menUsed:" + result[1]);
return result;
}


在一个线程（假设1毫秒一次）中，无限循环执行上面的代码：



大概20分钟左右后出现如下异常：



java.io.IOException: Cannot run program "free": java.io.IOException: error=24, Too many open files
        at java.lang.ProcessBuilder.start(ProcessBuilder.java:459)
        at java.lang.Runtime.exec(Runtime.java:593)
        at java.lang.Runtime.exec(Runtime.java:431)
        at java.lang.Runtime.exec(Runtime.java:328)
        at LinuxSystemTool.getMemUsage(LinuxSystemTool.java:98)
        at LinuxSystemTool.exec(LinuxSystemTool.java:67)
        at LinuxSystemTool.run(LinuxSystemTool.java:42)
        at java.lang.Thread.run(Thread.java:619)
Caused by: java.io.IOException: java.io.IOException: error=24, Too many open files
        at java.lang.UNIXProcess.<init>(UNIXProcess.java:148)
        at java.lang.ProcessImpl.start(ProcessImpl.java:65)
        at java.lang.ProcessBuilder.start(ProcessBuilder.java:452)
        ... 7 more



查看网络相关资料，大概了解可能是由于打开的句柄过多造成，也没有找到解决办法，不吝赐教，谢谢