Develop Reference

Sending 'exec' commands to Docker container using Java

I'm trying to send docker commands using Java Runtime.
Commands like docker cp works very nice with the below method as well as typing directly from the terminal.
First problem is that the docker exec command works only from the terminal, not with the Java Runtime. Other docker commands like docker cp works as expected. The only problem is that I can't run commands on the container, like echoing on the container's terminal.
Also the 2nd problem is that the System.out.println(...)method in the below method, doesn't actually print anything.
private static void runCommand() throws IOException, InterruptedException {
Process proc = Runtime.getRuntime().exec(
new String[]{"/bin/sh",
"-c",
"docker exec -u 0 -it <CONTAINER_NAME> echo", "'abc'"});
BufferedReader reader =
new BufferedReader(new InputStreamReader(proc.getInputStream()));
String line = "";
while ((line = reader.readLine()) != null) {
System.out.print(line + "\n");
}
proc.waitFor();
}

There is no need to run docker inside a shell. You can start the process directly.
As of Java 1.7 you can also use ProcessBuilder.inheritIO() to redirect the standard I/O of the subprocess
Below a working example that prints the output of the echo command:
ProcessBuilder processBuilder = new ProcessBuilder();
processBuilder.command("docker", "exec" , "-it", "<CONTAINER_NAME_OR_ID>", "echo", "abc").inheritIO();
try {
Process process = processBuilder.start();
BufferedReader reader = new BufferedReader(new InputStreamReader(process.getInputStream()));
String line;
while ((line = reader.readLine()) != null) {
System.out.println(line);
}
int exitCode = process.waitFor();
System.out.println("\nExited with error code : " + exitCode);
} catch (Exception e) {
e.printStackTrace();
}
Hope this helps.

How to execute cmd line of psexec and log to text file in a single line using JAVA?

I am trying to execute the following line in java(with escaped characters):
"psexec -i -d \\\\computerName -u user -p pass calc 2>
somePath\\psexecOut.txt"
I use the following method to execute cmd lines:
private static String executeCommand(String command) {
StringBuffer output = new StringBuffer();
System.out.println("command is = \n"+command);
Process p;
try {
p = Runtime.getRuntime().exec(command);
p.waitFor();
BufferedReader reader =
new BufferedReader(new InputStreamReader(p.getInputStream()));
String line = "";
while ((line = reader.readLine())!= null) {
output.append(line + "\n");
}
} catch (Exception e) {
e.printStackTrace();
}
return output.toString();
}
The line is executed and calc is starting , but the log part doesn't work. The log file psexecOut.txt is not created.
When I run the command normally (without excaped characters) in cmd it runs fine and the log file is created, but using java it doesn't create the log file.
I suspect that > needs to be escaped but as I read it's already escaped as it is.
How can I execute the psexec with log to text file in a single cmd line using java like I can do manually in windows console ?

Solved:
As lit suggested in the comments: cmd.exe /c works.
So the corrected method is:
private static String executeCommand(String command) {
StringBuffer output = new StringBuffer();
System.out.println("command is = \n"+command);
Process p;
try {
p = Runtime.getRuntime().exec("cmd.exe /c "+command); // <-correction done here
p.waitFor();
BufferedReader reader =
new BufferedReader(new InputStreamReader(p.getInputStream()));
String line = "";
while ((line = reader.readLine())!= null) {
output.append(line + "\n");
}
} catch (Exception e) {
e.printStackTrace();
}
return output.toString();
}

Try putting cmd.exe /C at the beginning of the command? It is cmd.exe that interprets the > redirection.
"cmd.exe /C psexec -i -d \\\\computerName -u user -p pass calc 2> somePath\\psexecOut.txt"

Java program not getting output from terminal

I am running my Java program from terminal and I am trying to count the number of files in a certain directory using a linux command in my code; I have managed to get output for all other commands but this one.
My command is: ls somePath/*.xml | wc -l
When I run my command in my code, it appears that it has nothing to output, yet when I run the same exact command in terminal it works just fine and actually outputs the number of xml files in that directory.
Here is my code:
private String executeTerminalCommand(String command) {
String s, lastOutput = "";
Process p;
try {
p = Runtime.getRuntime().exec(command);
BufferedReader br = new BufferedReader(
new InputStreamReader(p.getInputStream()));
System.out.println("Executing command: " + command);
while ((s = br.readLine()) != null){//it appears that it never enters this loop since I never see anything outputted
System.out.println(s);
lastOutput = s;
}
p.waitFor();
p.destroy();
} catch (Exception e) {
e.printStackTrace();
}
return lastOutput;//returns empty string ""
}
Updated code w/ output
private String executeTerminalCommand(String command) {
String s, lastOutput = "";
try {
Process p = new ProcessBuilder().command("/bin/bash", "-c", command).inheritIO().start();
//Process p = Runtime.getRuntime().exec(command);
BufferedReader br = new BufferedReader(
new InputStreamReader(p.getInputStream()));
System.out.println("Executing command: " + command);
while ((s = br.readLine()) != null){
System.out.println("OUTPUT: " + s);
lastOutput = s;
}
System.out.println("Done with command------------------------");
p.waitFor();
p.destroy();
} catch (Exception e) {
e.printStackTrace();
}
System.out.println("LAST OUTPUT IS: " + lastOutput);
return lastOutput;
}
output:
Executing command: find my/path -empty -type f | wc -l
Done with command------------------------
1
LAST OUTPUT IS:

To execute a pipeline, you have to invoke a shell, and then run your commands inside that shell.
Process p = new ProcessBuilder().command("bash", "-c", command).start();
bash invokes a shell to execute your command and -c means commands are read from string. So, you don't have to send the command as an array in ProcessBuilder.
But if you want to use Runtime then
String[] cmd = {"bash" , "-c" , command};
Process p = Runtime.getRuntime().exec(cmd);
Note: You can check advantages of ProcessBuilder here and features here over Runtime

java run bash script, command not found

I tried to use java to run some bash script and store the terminal output in a string. However, there are a lot of commands don't work in this way. It keeps showing command not found, but I can run those commands correctly in terminal, ex node --version, go --version. I guess is the path issue, but have no idea how to fix it.
Another question, when I run "python --version", it shows "Python 2.7.10" but it is in getErrorStream. Can anyone give me some hint?
public static void runscript() throws IOException {
Runtime rt = Runtime.getRuntime();
String[] commands = { "/bin/bash", "-c", "node --version" };
Process proc = null;
try {
proc = rt.exec(commands);
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
BufferedReader stdInput = new BufferedReader(new InputStreamReader(proc.getInputStream()));
BufferedReader stdError = new BufferedReader(new InputStreamReader(proc.getErrorStream()));
// read the output from the command
System.out.println("Here is the standard output of the command:\n");
String s = null;
while ((s = stdInput.readLine()) != null) {
System.out.println(s);
}
// read any errors from the attempted command
System.out.println("Here is the standard error of the command (if any):\n");
while ((s = stdError.readLine()) != null) {
System.out.println(s);
}
}

Reply #VishalKamat comment.
when I tried using the output of "which node" as my path, which is "/usr/local/bin/node". It works!!!
But, does that mean I have to change the path when I need to get different application version info?
I thought I can easily get the info just like I do in terminal.
I try to print $PATH by java in this way
String[] commands = { "/bin/bash","-c", "$PATH" };
The error msg is :
/bin/bash: /usr/bin:/bin:/usr/sbin:/sbin: No such file or directory

Runtime exec sh does nothing

So I want to execute sh script from java
Code:
String command = "/__data/1.sh";
ProcessBuilder pb = new ProcessBuilder("/bin/bash", "-c", command);
Process p = null;
try {
p = pb.start();
} catch (IOException e) {
System.out.println("Could not execute script");
}
BufferedReader reader = new BufferedReader(new InputStreamReader(
p.getInputStream()));
try {
String line = null;
while ((line = reader.readLine()) != null) {
System.out.println(command + " says: " + line);
}
} catch (IOException e) {
System.out.println("Error reading response");
}
1.sh:
echo Hello
mkdir QWE
echo Hello2
What I got:
/__data/1.sh says: Hello
/__data/1.sh says: Hello2
Mkdir takes no effect
1.sh chmodded to 777
What's the problem?
UPD: oh, my fault, forgot the line, now edited. But the main question is why other commands do not work. Yea, like mkdir.
When I call /bin/bash -c /__data/1.sh from console it works propertly
UPD: oh, it seems, mkdir doesn't work propertly because I did not set full path. Sorry. Solved

You're missing + line at the end of println. That should at least get rid of some of the confusion. Not sure why mkdir isn't working though.