Java执行Linux命令

Question

I want to write a java code that executes some Linux command:

String cmd = "cd /home/arps/FBI" ;

Process p=Runtime.getRuntime().exec(cmd);


String [] arr = new String [9] ;
 arr[0] = "cd /home/arps/FBI" ;
 for(int n = 1 ; n < 9 ; n++){
 String command = "mv" + "  " +  "/home/arps/FBI/hr" + n + ".txt" + "    " + "/home/arps/FBI/hrs" + n +".txt" ;
 arr[n] = command ;
}


 Process pp=Runtime.getRuntime().exec(arr);

In above code: I try to rename 8 files named hr1, hr2 .... to hrs1 , hrs2 ... etc. In cd command I try to enter the required directory. However, I have used absolute path also. But the code is giving error:

java.io.IOException: Cannot run program "cd": java.io.IOException: error=2, No such file or directory

java.io.IOException: Cannot run program "mv  /home/arps/FBI/hr1.txt    /home/arps/FBI/hrs1.txt": java.io.IOException: error=2, No such file or directory

Can anybody help me why is this happening though I manually execute those command means "mv /home/arps/FBI/hr1.txt /home/arps/FBI/hrs1.txt" and executes properly?

Answer 1

cd is a built-in command to the current shell - you can't execute it - it's a shell built-in, as the cwd is a process-level setting, so a new process has it's own value. There is no way to change the cwd from within the java process.

The array argument version of exec is for executing a single command, where you have split the arguments yourself, not for executing multiple commands.

So you either need to give full paths, or implement the copy yourself in Java.

Answer 2

Change the final line of your program from

Process pp=Runtime.getRuntime().exec(arr);

to:

 for (String cmdLine: arr) {
    Process pp=Runtime.getRuntime().exec(cmdLine);

and you will execute each line separately, according to RunTime documentation .

Answer 3

您最好编写一个满足您需要的shell脚本，然后从Java调用它。

Answer 4

arr array must store the arguments of command. Not seperated commands. refer to my question. run shell command from java

Answer 5

If ls -l /home/arps/FBI/hrs1.txt outputs nothing as you said in the comments, then the file you're trying to rename simply does not exist, so the exception is right about this.

PS: IMHO this is not to be done in Java. Use scripting languages for such things. Way easier and way smaller code. For each problem, try to use the right tool, not one tool for all problems.