Unable to run a shell script from java

Question

I have a shell script that has a single command to generate a file with the required information in it after sucessful creation of the script.

Now when Iam executing that command directly or executing the script itself from the cmd line the file is getting generated.

But when iam trying to execute the same script from the java code using Runtime.getRuntime().exec(cmd) the file is not getting generated.The traces just before and after this line are displayed as expected indicated that the execution of the script is not throwing any exceptions.

Where am I going wrong or what am I missing on? Plz help!!!

Example this is the code iam tryng to execute

import java.io.BufferedReader;
import java.io.InputStreamReader;

public class Scripttest {
public static void main(String args[])
{
        try{
String cmd="ls|grep sys";
        Process p=Runtime.getRuntime().exec(cmd);
        System.out.println("done");
        final BufferedReader input = new BufferedReader(new InputStreamReader( p.getInputStream()));
        String line = null;
        while ((line = input.readLine()) != null)
         System.out.println("proc: " + line);
}
        catch(Exception e)
        {
                System.out.println("Exception is"+e);
        }
}
}

and the output iam getting is this

java Scripttest
Exception isjava.io.IOException: Cannot run program "ls|grep": error=2, No such file or directory

The cmd is not getting executed but not sure abt the mistake why it is not.

you can see the error if any by getting the ErrorOutputStream and see what is the error .. — Hemant Metalia, Jun 28 '12 at 07:02
What is the value of `cmd`? Are you sure you have escaped any backslashes etc? — kjp, Jun 28 '12 at 07:03
working directory? relative or absolute path? Perhaps showing us `cmd` would help... — John3136, Jun 28 '12 at 07:06
also see this answer: http://stackoverflow.com/a/526287/390913 — perreal, Jun 28 '12 at 07:07
because ls|grep is a not a program, it is what you typed and interpreted by bash which is a program. — pizza, Jun 28 '12 at 17:43

score 2 · Answer 1 · answered Jun 28 '12 at 08:06

Here is an example to do it somewhat like using pipes, the script is embedded in java in this example.

import java.io.*;
class junk {
 public static void main (String args[]) {
  try {
   String line; String script;
   OutputStream stdin = null; InputStream stderr = null; InputStream stdout = null;
   Process p = Runtime.getRuntime ().exec ("/bin/bash");
   stdin = p.getOutputStream (); stderr = p.getErrorStream (); stdout = p.getInputStream ();
   script = "a=$(cat <<'@@@'\n" +
"ICAgICBfCiAgICB8IHwgX18gX19fICAgX19fXyBfICAgIF9fXyBfXyBfIF8gX18gICAgXyBfXyBfICAg" +
"XyBfIF9fCiBfICB8IHwvIF9gIFwgXCAvIC8gX2AgfCAgLyBfXy8gX2AgfCAnXyBcICB8ICdfX3wgfCB8" +
"IHwgJ18gXAp8IHxffCB8IChffCB8XCBWIC8gKF98IHwgfCAoX3wgKF98IHwgfCB8IHwgfCB8ICB8IHxf" +
"fCB8IHwgfCB8CiBcX19fLyBcX18sX3wgXF8vIFxfXyxffCAgXF9fX1xfXyxffF98IHxffCB8X3wgICBc" +
"X18sX3xffCB8X3wKICAgICAgICAgICAgICAgICAgICBfICAgICAgICAgICAgICAgXwogICAgICAgICAg" +
"ICAgICAgICAgfCB8X18gICBfXyBfIF9fX3wgfF9fCiAgICAgICAgICAgICAgICAgICB8ICdfIFwgLyBf" +
"YCAvIF9ffCAnXyBcCiAgICAgICAgICAgICAgICAgICB8IHxfKSB8IChffCBcX18gXCB8IHwgfAogICAg" +
"ICAgICAgICAgICAgICAgfF8uX18vIFxfXyxffF9fXy9ffCB8X3wK" +
"\n" +
"@@@)\n" +
"st=0\n" +
"for (( i=0; i<\"${#a}\"; i++ ))\n" +
"do\n" +
" x=${a:$i:1}\n" +
" in=$(($(expr index \\\n" +
" 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/' \"\\\\$x\")-1))\n" +
" if [ $in -ge 0 ]; then case $st in\n" +
"  0 ) out=$(($in<<2)); st=3;;\n" +
"  1 ) out=$(($out|$in)); \n" +
"    printf \\\\$(printf '%03o' $(($out&255)) ) ; st=0 ;;\n" +
"  2 ) out=$(($out+($in>>2))); \n" +
"    printf \\\\$(printf '%03o' $(($out&255)) ) ;\n" +
"    st=0; out=$(($in<<6)); st=1;;\n" +
"  * ) out=$(($out+($in>>4))); \n" +
"    printf \\\\$(printf '%03o' $(($out&255)) ) ;\n" +
"    st=0; out=$(($in<<4)); st=2;;\n" +
"  esac fi\n" +
"done\n";
   stdin.write (script.getBytes ());
   stdin.close ();
   BufferedReader br = new BufferedReader (new InputStreamReader (stdout));
   while ((line = br.readLine ()) != null) { System.out.println(line); }
   br.close ();
   br = new BufferedReader (new InputStreamReader (stderr));
   while ((line = br.readLine ()) != null) { System.out.println ("2>" + line); }
   br.close ();
   p.waitFor ();
   System.out.println ("exit code " + p.exitValue ());
  }
  catch (IOException e) { e.printStackTrace (); }
  catch (java.lang.InterruptedException e) { e.printStackTrace (); }
 }
}

score 0 · Answer 2 · answered Feb 08 '13 at 05:30

keep the command ls|grep sys in an array because It consists of two primary commands ls and grep.

Or

The best idea is to use shell script in linux and batch file in windows. create a shell script or batch file as per your requirement with the commands and just execute the shell script or batch file from java code.

Unable to run a shell script from java

2 Answers2