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java command execution escapes '|'

I have a function to execute a system command:
public String cmd(String s) {
String out = "";
try {
Runtime run = Runtime.getRuntime();
Process pr = run.exec(s.split(" "));
pr.waitFor();
BufferedReader buf = new BufferedReader(new InputStreamReader(pr.getInputStream()));
String line = "";
while ((line=buf.readLine())!=null) {
out+=line+"\n";
}
} catch(Exception e) {
e.printStackTrace();
}
return out;
}
The command passes through:
cmd("nmap -sL -n 192.168.1.0/24 | awk '/Nmap scan report/{print $NF}'");
Expected Output:
192.168.1.0
192.168.1.1
...
Actual Output:
Starting Nmap 7.80 ( https://nmap.org ) at 2021-04-12 20:27 EET
Nmap scan report for 192.168.1.0 ...

Similar questions answers this well:
Using Java ProcessBuilder to Execute a Piped Command
Java program not getting output from terminal
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.
Adapted to you case
String cmd(String command) {
ProcessBuilder builder = new ProcessBuilder();
builder.redirectErrorStream(true); // add stdErr to output
Process process = builder.command("bash", "-c", command).start();
StringBuilder processOutput = new StringBuilder(); // add lines easier
// try-with to auto-close resources
try (BufferedReader processOutputReader = new BufferedReader(new InputStreamReader(process.getInputStream()));) {
String readLine;
while ((readLine = processOutputReader.readLine()) != null) {
processOutput.append(readLine + System.lineSeparator()); // use system's line-break
}
process.waitFor();
}
return processOutput.toString().trim();
}
Then call as expected:
cmd("nmap -sL -n 192.168.1.0/24 | awk '/Nmap scan report/{print $NF}'");
Note: I enhanced it a bit to
use try-with-resources to deal cleanly with resources
add output from StdErr
use a StringBuilder to concatenate output lines
use System.lineSeparator for platform-independency (Win/Mac/Linux/Unix)
Inspired by:
read the output from java exec

The pipe is interpreted by the shell. It executes one command then passes the output of one command into the next one. You could emulate this in Java starting both commands and then pumping the OutputStream of the first program to the InputStream of the second.
Alternatively if you don't want to do this you can still call something like "sh -c 'command1 | command2"

How do I run GDB and accept GDB commands through Java output console?

I am trying to build a GUI for GCC which has some basic functionalities like compile, link, execute, debug, etc for C++ programs using Java. I am creating strings of command which I pass to the ProcessBuilder and run it via command prompt and GCC.
command = "cd src & cd Resources & g++ " + compileFile.cpp +" -Wall "+ " -o "+ "tempOut";
This is a sample code for compiling the file.
Part of this is the debug functionality for which I am using GDB. Now the problem is GDB needs additional input to add breakpoints, remove breakpoints and so on. I am having trouble on how to pass these necessary inputs to GDB via Java terminal. If I pass the commands in the command prompt, it is working fine and I get the desired output.
enter image description here
But whenever I fire the GDB command from the Java program, I cannot pass any inputs from the IDE's terminal. I am aware that each GDB command uses a different process and I tried attaching Java's process ID to GDB but I just get a blank output console. It seems that the GDB session has started but there is no way to interact with that process through the IDE's output console.
int pid = Integer.parseInt(ManagementFactory.getRuntimeMXBean().getName().split("#")[0]);
command = "gdb attach "+ pid;
fireCommand();
EDIT
This is the method that interacts with command prompt to take input and display output in the IDE's output console:
public void fireCommand() {
String line;
String os = System.getProperty("os.name");
ProcessBuilder builder;
if(os.startsWith("Win")) {
builder = new ProcessBuilder("cmd.exe", "/c", command);
}
else{
builder = new ProcessBuilder("bash", "-c", command);
}
try {
process = builder.start();
BufferedReader reader = new BufferedReader(
new InputStreamReader(process.getInputStream()));
while ((line = reader.readLine()) != null) {
if(line.contains("Input the value")) {
//any other user input in non debug execution
String value = JOptionPane.showInputDialog(line);
BufferedWriter writer = new BufferedWriter(
new OutputStreamWriter(process.getOutputStream()));
writer.write(value, 0, value.length());
writer.newLine();
writer.close();
}
else {
output.append(line).append("\n");
}
}
int exitVal = process.waitFor();
if (exitVal == 0) {
//display("Success!");
display(output.toString());
} else {
String lineErr;
BufferedReader readerErr = new BufferedReader(
new InputStreamReader(process.getErrorStream()));
while ((lineErr = readerErr.readLine()) != null) {
outputErr.append(lineErr).append("\n");
}
//display(exitVal);
display(outputErr.toString()); //Display the uncatched errors
}
} catch (IOException e) {
display("There was a problem with the I/O");
e.printStackTrace();
} catch (InterruptedException e) {
display("There was a interruption with the execution");
e.printStackTrace();
}
if(!outputErr.toString().isEmpty())
errorFormatDisplay(); //display Error output function
}
Any leads on this would be very helpful. Thank you.

I am aware that each GDB command uses a different process
No, gdb runs as one process. Did you mean to say that you are creating a new gdb process every time you try to pass it a gdb command ?
It seems that the GDB session has started but there is no way to interact with that process through the IDE's output console.
Maybe you should use The GDB/MI Interface, which e.g. the Emacs debugger mode gud uses.

Excute bash script "ps aux | wc -l" in java response empty result [duplicate]

Consider the following code:
String commandf = "ls /etc | grep release";
try {
// Execute the command and wait for it to complete
Process child = Runtime.getRuntime().exec(commandf);
child.waitFor();
// Print the first 16 bytes of its output
InputStream i = child.getInputStream();
byte[] b = new byte[16];
i.read(b, 0, b.length);
System.out.println(new String(b));
} catch (IOException e) {
e.printStackTrace();
System.exit(-1);
}
The program's output is:
/etc:
adduser.co
When I run from the shell, of course, it works as expected:
poundifdef#parker:~/rabbit_test$ ls /etc | grep release
lsb-release
The internets tell me that, due to the fact that pipe behavior isn't cross-platform, the brilliant minds who work in the Java factory producing Java can't guarantee that pipes work.
How can I do this?
I am not going to do all of my parsing using Java constructs rather than grep and sed, because if I want to change the language, I'll be forced to re-write my parsing code in that language, which is totally a no-go.
How can I make Java do piping and redirection when calling shell commands?

Write a script, and execute the script instead of separate commands.
Pipe is a part of the shell, so you can also do something like this:
String[] cmd = {
"/bin/sh",
"-c",
"ls /etc | grep release"
};
Process p = Runtime.getRuntime().exec(cmd);

I ran into a similar problem in Linux, except it was "ps -ef | grep someprocess".
At least with "ls" you have a language-independent (albeit slower) Java replacement. Eg.:
File f = new File("C:\\");
String[] files = f.listFiles(new File("/home/tihamer"));
for (String file : files) {
if (file.matches(.*some.*)) { System.out.println(file); }
}
With "ps", it's a bit harder, because Java doesn't seem to have an API for it.
I've heard that Sigar might be able to help us:
https://support.hyperic.com/display/SIGAR/Home
The simplest solution, however, (as pointed out by Kaj) is to execute the piped command as a string array. Here is the full code:
try {
String line;
String[] cmd = { "/bin/sh", "-c", "ps -ef | grep export" };
Process p = Runtime.getRuntime().exec(cmd);
BufferedReader in =
new BufferedReader(new InputStreamReader(p.getInputStream()));
while ((line = in.readLine()) != null) {
System.out.println(line);
}
in.close();
} catch (Exception ex) {
ex.printStackTrace();
}
As to why the String array works with pipe, while a single string does not... it's one of the mysteries of the universe (especially if you haven't read the source code). I suspect that it's because when exec is given a single string, it parses it first (in a way that we don't like). In contrast, when exec is given a string array, it simply passes it on to the operating system without parsing it.
Actually, if we take time out of busy day and look at the source code
(at http://grepcode.com/file/repository.grepcode.com/java/root/jdk/openjdk/6-b14/java/lang/Runtime.java#Runtime.exec%28java.lang.String%2Cjava.lang.String[]%2Cjava.io.File%29), we find that is exactly what is happening:
public Process [More ...] exec(String command, String[] envp, File dir)
throws IOException {
if (command.length() == 0)
throw new IllegalArgumentException("Empty command");
StringTokenizer st = new StringTokenizer(command);
String[] cmdarray = new String[st.countTokens()];
for (int i = 0; st.hasMoreTokens(); i++)
cmdarray[i] = st.nextToken();
return exec(cmdarray, envp, dir);
}

Create a Runtime to run each of the process. Get the OutputStream from the first Runtime and copy it into the InputStream from the second one.

#Kaj accepted answer is for linux. This is the equivalent one for Windows:
String[] cmd = {
"cmd",
"/C",
"dir /B | findstr /R /C:"release""
};
Process p = Runtime.getRuntime().exec(cmd);

How to make pipes work with Runtime.exec()?

Consider the following code:
String commandf = "ls /etc | grep release";
try {
// Execute the command and wait for it to complete
Process child = Runtime.getRuntime().exec(commandf);
child.waitFor();
// Print the first 16 bytes of its output
InputStream i = child.getInputStream();
byte[] b = new byte[16];
i.read(b, 0, b.length);
System.out.println(new String(b));
} catch (IOException e) {
e.printStackTrace();
System.exit(-1);
}
The program's output is:
/etc:
adduser.co
When I run from the shell, of course, it works as expected:
poundifdef#parker:~/rabbit_test$ ls /etc | grep release
lsb-release
The internets tell me that, due to the fact that pipe behavior isn't cross-platform, the brilliant minds who work in the Java factory producing Java can't guarantee that pipes work.
How can I do this?
I am not going to do all of my parsing using Java constructs rather than grep and sed, because if I want to change the language, I'll be forced to re-write my parsing code in that language, which is totally a no-go.
How can I make Java do piping and redirection when calling shell commands?

Write a script, and execute the script instead of separate commands.
Pipe is a part of the shell, so you can also do something like this:
String[] cmd = {
"/bin/sh",
"-c",
"ls /etc | grep release"
};
Process p = Runtime.getRuntime().exec(cmd);

I ran into a similar problem in Linux, except it was "ps -ef | grep someprocess".
At least with "ls" you have a language-independent (albeit slower) Java replacement. Eg.:
File f = new File("C:\\");
String[] files = f.listFiles(new File("/home/tihamer"));
for (String file : files) {
if (file.matches(.*some.*)) { System.out.println(file); }
}
With "ps", it's a bit harder, because Java doesn't seem to have an API for it.
I've heard that Sigar might be able to help us:
https://support.hyperic.com/display/SIGAR/Home
The simplest solution, however, (as pointed out by Kaj) is to execute the piped command as a string array. Here is the full code:
try {
String line;
String[] cmd = { "/bin/sh", "-c", "ps -ef | grep export" };
Process p = Runtime.getRuntime().exec(cmd);
BufferedReader in =
new BufferedReader(new InputStreamReader(p.getInputStream()));
while ((line = in.readLine()) != null) {
System.out.println(line);
}
in.close();
} catch (Exception ex) {
ex.printStackTrace();
}
As to why the String array works with pipe, while a single string does not... it's one of the mysteries of the universe (especially if you haven't read the source code). I suspect that it's because when exec is given a single string, it parses it first (in a way that we don't like). In contrast, when exec is given a string array, it simply passes it on to the operating system without parsing it.
Actually, if we take time out of busy day and look at the source code
(at http://grepcode.com/file/repository.grepcode.com/java/root/jdk/openjdk/6-b14/java/lang/Runtime.java#Runtime.exec%28java.lang.String%2Cjava.lang.String[]%2Cjava.io.File%29), we find that is exactly what is happening:
public Process [More ...] exec(String command, String[] envp, File dir)
throws IOException {
if (command.length() == 0)
throw new IllegalArgumentException("Empty command");
StringTokenizer st = new StringTokenizer(command);
String[] cmdarray = new String[st.countTokens()];
for (int i = 0; st.hasMoreTokens(); i++)
cmdarray[i] = st.nextToken();
return exec(cmdarray, envp, dir);
}

Create a Runtime to run each of the process. Get the OutputStream from the first Runtime and copy it into the InputStream from the second one.

#Kaj accepted answer is for linux. This is the equivalent one for Windows:
String[] cmd = {
"cmd",
"/C",
"dir /B | findstr /R /C:"release""
};
Process p = Runtime.getRuntime().exec(cmd);

Printing my Mac's serial number in java using Unix commands

I am trying to print my mac's [edit: Apple computer] serial number in a java program. I am familiar with the Unix command
ioreg -l | awk '/IOPlatformSerialNumber/ { print $4;}'
which accomplishes this task in terminal.
When I try
String command = "ioreg -l | awk '/IOPlatformSerialNumber/ { print $4; }'"
Runtime terminal = Runtime.getRuntime();
String input = new BufferedReader(
new InputStreamReader(
terminal.exec(commands).getInputStream())).readLine();
System.out.println(new BufferedReader(
new InputStreamReader(
terminal.exec(command, args).getInputStream())).readLine());
my serial number is not printed. Instead it prints:
<+-o Root class IORegistryEntry, id 0x100000100, retain 10>
I think the problem is that terminal.exec() is not meant to take the whole command string. Is there something in java similar to the argument shell = True in python's Popen(command, stdout=PIPE, shell=True) that will allow me to pass the whole command string?

I see two possibilities:
Parse the output of ioreg -l using, say, Scanner.
Wrap the command in a shell script and exec() it:
#!/bin/sh
ioreg -l | awk '/IOPlatformSerialNumber/ { print $4;}'
Addendum: As an example of using ProcessBuilder, and incorporating a helpful suggestion by Paul Cager, here's a third alternative:
import java.io.BufferedReader;
import java.io.InputStreamReader;
public class PBTest {
public static void main(String[] args) {
ProcessBuilder pb = new ProcessBuilder("bash", "-c",
"ioreg -l | awk '/IOPlatformSerialNumber/ { print $4;}'");
pb.redirectErrorStream(true);
try {
Process p = pb.start();
String s;
// read from the process's combined stdout & stderr
BufferedReader stdout = new BufferedReader(
new InputStreamReader(p.getInputStream()));
while ((s = stdout.readLine()) != null) {
System.out.println(s);
}
System.out.println("Exit value: " + p.waitFor());
p.getInputStream().close();
p.getOutputStream().close();
p.getErrorStream().close();
} catch (Exception ex) {
ex.printStackTrace();
}
}
}

Pipes aren't supported by Runtime.exec(..) since they are a feature of shells. Instead, you'd have to emulate the pipe yourself, e.g.
String ioreg = toString(Runtime.exec("ioreg -l ").getInputStream());
Process awk = Runtime.exec("awk '/IOPlatformSerialNumber/ { print $4;}'");
write(awk.getOutputStream(), ioreg);
String input = new BufferedReader(new InputStreamReader(awk.getInputStream())).readLine();
Alternatively, you could of course run a shell as a process, e.g. Runtime.exec("bash"), and interact with it by reading and writing its IO streams. Interacting with processes is a bit tricky though and has some gotchas and let it execute your command (see comments)

To get the MAC addres via Java you can use java.net.NetworkInterface:
NetworkInterface.getByName("xxx").getHardwareAddress()
If you don't know the name (I assume it to be 'eth0' on linux) of your network interface, you can even iterate throug all of your network interfaces using NetworkInterface.getNetworkInterfaces().