Develop Reference

Run a compound shell command from Java/Groovy

I got stuck trying to run a compound shell command from a Groovy script. It was one of those commands where you separate with "&&" so that the 2nd command never runs if the 1st one fails. For whatever reason I couldn't get it to work. I was using:
println "custom-cmd -a https://someurl/path && other-cmd -f parameter".execute([], new File('/some/dir')).text
The shell kept misinterpreting the command throwing errors like "custom-cmd -f invalid option" It was like it was ignoring the "&&" in between. I tried using a semi-colon as well but was not lucky. I tried using straight Java APIs Runtime.getRuntime().exec() and splitting the command into an array. I tried wrapping the command in single quotes and giving it to '/bin/sh -c' but nothing works.
How do you run a compound shell command from Java? I know I've done this in the past but I cannot figure it out today.

With groovy, the list form of execute should work:
def out = ['bash', '-c', "custom-cmd -a https://someurl/path && other-cmd -f parameter"].execute([], new File('/some/dir')).text
Of course you may want to use the consumeProcessOutput method on process, as if the output is too large, calling text may block

Try something like:
Runtime.getRuntime().exec("cmd /c \"start somefile.bat && start other.bat && cd C:\\test && test.exe\"");
Runtime.getRuntime().exec() can be used without splitting the commands into an array.
see https://stackoverflow.com/a/18867097/1410671
EDIT:
Have you tried using a ProcessBuilder? This seems to work on my OSX box:
public static void main(String[] args) throws IOException {
ProcessBuilder builder = new ProcessBuilder( "/bin/sh", "-c", "echo '123' && ls" );
Process p=null;
try {
p = builder.start();
}
catch (IOException e) {
System.out.println(e);
}
Scanner s = new Scanner( p.getInputStream() );
while (s.hasNext())
{
System.out.println( s.next() );
}
s.close();
}

Redirecs with /bin/bash from Java Runtime exec()

I'm trying to use a redirect in a command executed with the exec()-method of java.lang.Runtime on Ubuntu 14.04
public static void main(String[] args) throws IOException, Exception {
Runtime runtime = Runtime.getRuntime();
String command = "echo bla > bla.txt";
System.out.println("Command : " + command);
Process process = runtime.exec(command);
printLines(" stdout", process.getInputStream());
printLines(" error", process.getErrorStream());
process.waitFor();
System.out.println("ExitValue : " + process.exitValue());
}
private static void printLines(String name, InputStream ins) throws Exception {
try(Stream<String> lines = new BufferedReader(new InputStreamReader(ins)).lines()) {
lines.forEach(line -> System.out.println(name + " : " + line));
}
}
The output is:
Command : echo bla > bla.txt
stdout : bla > bla.txt
ExitValue : 0
So bla > bla.txt is written to stdout but of course there is no redirect to bla.txt.
Perhapes shell redirects are not possible in a simple exec().
So I tried to change the command = "/bin/bash -c 'echo bla > bla.txt'" to use the whole echo and redirect as a parameter to /bin/bash.
With this I get the result:
Command : /bin/bash -c 'echo bla > bla.txt'
error : bla: -c: line 0: unexpected EOF while looking for matching `''
error : bla: -c: line 1: syntax error: unexpected end of file
ExitValue : 1
Of course /bin/bash -c 'echo bla > bla.txt'works fine on Ubuntu and creates the desired file.
I found no place where I could set the single quotes to get a satisfying result, and I also tried with all kinds of escape characters to escape the spaces or the redirect (>).
It works if I use a command array like
String cmdArray[] = {"/bin/bash", "-c", "echo bla > bla.txt"};
Process process = runtime.exec(cmdArray);
, but it has to be a single string because the entire command has to be build somewhere else.
I surely know
that there are better ways to write strings to files,
that it may be a bad idea to execute commands build somewhere else,
and so on ...
I'm just curious why this does not work.

The cause is that exec uses simple StringTokenizer with any white space as a delimiter to parse the actual command. Therefore it's portable as it does work nowhere when you pass something complex :-)
The workaround you chose is correct way, portable and most of all safest asyou ddon't need to escape if the command contained for example quotes etc.

String command = "echo bla > bla.txt";
Process process = runtime.exec(command);
The > blah.txt text in your command is shell syntax to redirect standard output. It's implemented by shells like sh or bash.
Runtime.exec() doesn't use a shell to run commands. The way it launches commands is described here and here. Basically, it uses its own logic to split the command string into arguments at spaces, then directly executes the resulting command.
If you want to invoke a command which should be interpreted as a shell command, you need to explicitly invoke a shell:
String[] command = { "/bin/bash", "-c", "echo bla > bla.txt" };
Process process = runtime.exec(command);

Executing Multi cmd Command using JAVA

Am trying to pop up a CMD then execute some Commands such as:
echo SOMETHING && echo SOMETHING && mkdir....etc
i managed to open the CMD but JAVA doesnt seem to recognize "&" inside string
the first command which before the "&" is the only being executed
any tips ?
try {
// Execute command
String command = "cmd /c start echo hello baby & echo the world";
Process child = Runtime.getRuntime().exec(command);
// Get output stream to write from it
} catch (IOException e) {
}
}
}

It's &&, not &.
A double ampersand is a logical "and", a single ampersand means "put the (first!) process into the background".
PS: By "cmd", do you mean the good ol' Windows cmd.exe? If yes, I don't know if those ampersands are working there. Try the PowerShell instead if so.

firing a command in terminal from java program

I need to write a java program which when executed pushes a command into the terminal
I tried using runtime.exec(); but not working fine for me
what i want is "/home/raj/Desktop/java -jar test.jar" to be executed in terminal
Can any one help me to sort it out.

If you want to actually start a terminal window (rather than just executing the java process) you will need to launch xterm (or something similar) and tell xterm to run java for example
String command= "/usr/bin/xterm -e /home/raj/Desktop/java -jar test.jar";
Runtime rt = Runtime.getRuntime();
Process pr = rt.exec(command);

Please refer following example .with list of arguments to java program.
Process proc = null;
try {
String cmd[] = {"gnome-terminal", "-x", "bash", "-c", "ls; echo '<enter>'; read" };
proc = Runtime.getRuntime().exec(cmd, null, wd);
} catch (IOException e) {
e.printStackTrace();
}

You can use full path of the jar file as an argument to "java"
String command= "java -jar /home/raj/Desktop/test.jar";
Runtime rt = Runtime.getRuntime();
Process pr = rt.exec(command);

Execute Unix system command from JAVA problem

I am facing a weird issue with executing a system command from JAVA code.
Actually i want to get the Mac OSX system information from my JAVA App.
For that im using
Runtime.getRuntime().exec("system_profiler -detailLevel full");
This is working fine.If i print the output,it is cool.
But i want to write this information to a plist file for future use.For that im using the -xml argument of system_profiler.like,
String cmd = "system_profiler -detailLevel full -xml > "+System.getProperty( "user.home" )+"/sysinfo.plist";
Process p = Runtime.getRuntime().exec(cmd);
Basically this should create a plist file in the current users home directory.
But this seems to be not writing anything to file.
Am i missing something here ?

My Java is more than rusty, so please be gentle. ;-)
Runtime.exec() does not automatically use the shell to execute the command you passed, so the IO redirection is not doing anything.
If you just use:
"/bin/sh -c system_profiler -detailLevel full > path/file.plist"
Then the string will be tokenized into:
{ "/bin/sh", "-c", "system_profiler", "-detailLevel", "full", ">", "path/file.plist" }
Which also wouldn't work, because -c only expects a single argument.
Try this instead:
String[] cmd = { "/bin/sh", "-c", "system_profiler -detailLevel full > path/file.plist" };
Process p = Runtime.getRuntime.exec(cmd);
Of course, you could also just read the output of your Process instance using Process.getInputStream() and write that into the file you want; thus skip the shell, IO redirection, etc. altogether.

Christian.K is absolutely correct. Here is a complete example:
public class Hello {
static public void main (String[] args) {
try {
String[] cmds = {
"/bin/sh", "-c", "ls -l *.java | tee tmp.out"};
Process p = Runtime.getRuntime().exec (cmds);
p.waitFor ();
System.out.println ("Done.");
}
catch (Exception e) {
System.out.println ("Err: " + e.getMessage());
}
}
}
If you weren't using a pipe (|) or redirect (>), then you'd be OK with String cmd = "ls -l *.java", as in your original command.
If you actually wanted to see any of the output in your Java console window, then you'd ALSO need to call Process.getInputStream().
Here's a good link:
Running system commands in Java applications