Develop Reference

Pipe ("|") doesn't work with ProcessBuilder in Android [duplicate]

I'm trying to use Java's ProcessBuilder class to execute a command that has a pipe in it. For example:
ls -l | grep foo
However, I get an error:
ls: |: no such file or directory
Followed by:
ls: grep: no such file or directory
Even though that command works perfectly from the command line, I can not get ProcessBuilder to execute a command that redirects its output to another.
Is there any way to accomplish this?

This should work:
ProcessBuilder b = new ProcessBuilder("/bin/sh", "-c", "ls -l| grep foo");
To execute a pipeline, you have to invoke a shell, and then run your commands inside that shell.

The simplest way is to invoke the shell with the command line as the parameter. After all, it's the shell which is interpreting "|" to mean "pipe the data between two processes".
Alternatively, you could launch each process separately, and read from the standard output of "ls -l", writing the data to the standard input of "grep" in your example.

Since Java 9, there’s genuine support for piplines in ProcessBuilder.
So you can use
List<String> result;
List<Process> processes = ProcessBuilder.startPipeline(List.of(
new ProcessBuilder("ls", "-l")
.inheritIO().redirectOutput(ProcessBuilder.Redirect.PIPE),
new ProcessBuilder("grep", "foo")
.redirectError(ProcessBuilder.Redirect.INHERIT)
));
try(Scanner s = new Scanner(processes.get(processes.size() - 1).getInputStream())) {
result = s.useDelimiter("\\R").tokens().toList();
}
to get the matching lines in a list.
Or, for Windows
List<String> result;
List<Process> processes = ProcessBuilder.startPipeline(List.of(
new ProcessBuilder("cmd", "/c", "dir")
.inheritIO().redirectOutput(ProcessBuilder.Redirect.PIPE),
new ProcessBuilder("find", "\"foo\"")
.redirectError(ProcessBuilder.Redirect.INHERIT)
));
try(Scanner s = new Scanner(processes.get(processes.size() - 1).getInputStream())) {
result = s.useDelimiter("\\R").tokens().toList();
}
These examples redirect stdin of the first process and all error streams to inherit, to use the same as the Java process.
You can also call .redirectOutput(ProcessBuilder.Redirect.INHERIT) on the ProcessBuilder of the last process, to print the results directly to the console (or wherever stdout has been redirected to).

complete CMD command not running from java

I am running the below query through Java on a Postgres DB using psql:
psql.exe -U <user> -w -h <host> -d <db_name> -a -f <file> 2> "<path_to_file>\psql.log"
Initially, for quite some time the java program did create the file. Then I ran into another problem, that it was not overwriting the log file. So i used file.delete() function after every time this log file got created via java.
Now, Java is not even creating the log file for some reason. If I run the above manually in command prompt, it runs absolutely fine, but not via java code. I can see this command getting run in the java log, but it does not create the log file even when i have removed the file.delete() function
I researched a lot on it but could not find any solution. Any help would be highly appreciated.
its a long code..so i will tell you the relevant part.
I am calling a function from a thread. Code is below for that function:
public static void SaveACopyfileToServer(int auditid,String filepath,String fname,String tb_name,String plpgsql_path) throws Exception
{
Map<String, String> env = System.getenv();
String plpgsql = "\""+plpgsql_path+"\" -U "+env.get("PG_USER")+" -w -h "+env.get("PG_HOST")+" -d "+env.get("PG_DB")+" -a -f "+"\""+filepath+"copy_"+tb_name+auditid+".sql\" 2> \"C:\\ER\\ETL\\logs\\psql.log\"";
System.out.println(plpgsql);
Process p = Runtime.getRuntime().exec(plpgsql);
p.getOutputStream().close();
p.waitFor();
SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss:SSS");
Calendar cal10 = Calendar.getInstance();
System.out.println("Data loaded for "+tb_name+auditid+" at "+sdf.format(cal10.getTime()));
}
After this i am calling another function which is:
public static void extracterrorreason(String fname,int auditid,String sessionid,Connection con_pg) throws FileNotFoundException, IOException, InterruptedException{
File file = new File("C:\\ER\\ETL\\logs\\psql.log");
if(file.exists())
{
System.out.println("File present");
}
else
{
System.out.println(file+" not found");
}
if (file.length()!=0){
System.out.println("Log file being read is "+file);
BufferedReader br = new BufferedReader(new FileReader(file));
String line = br.readLine();
String out_err = line.substring(line.indexOf("ERROR"));
System.out.println(out_err);
System.out.println("Error while loading the file into Database for file "+fname);
String comment = "CopyToStage','"+out_err;
Utils.updateAuditDetailTable(auditid, sessionid, -1, comment, true, con_pg,"");
br.close();
//file.delete();
}
}
The first function used to create the psql.log file, but now it does not even create it. Not sure where is the problem. Every time i run the code and from the second function,i get the printline that log file not found. The part before the redirection of the output of the cmd command works fine.
I tried process builder also..
I even tried it with Process builder
String plpgsql = "\""+plpgsql_path+"\" -U "+env.get("PG_USER")+" -w -h "+env.get("PG_HOST")+" -d "+env.get("PG_DB")+" -a -f "+"\""+filepath+"copy_"+tb_name+auditid+".sql\" 2> \"C:\\ER\\ETL\\psql_" +auditid +".log\"";
ProcessBuilder pb = new ProcessBuilder("cmd.exe",plpgsql);
Process p =pb.start();
p.getOutputStream().close();
p.waitFor();

I expect that the problem is that Runtime.getRuntime().exec(plpgsql) is splitting the command line into arguments incorrectly. Basically, exec does not understand quoting. Instead, it splits wherever it sees one or more spaces ... even if those spaces are in quotes.
The solution is to use the exec(String[]) overload, and pass each individual argument as a separate string; e.g.
.exec(new String[]{plpgsql_path,
"-U",
env.get("PG_USER"),
"-w,
"-h",
// etcetera
});
UPDATE
I didn't notice that you were using > output redirection as well1.
That doesn't work with exec either. (And the same applies to all shell syntax.) To get redirection, you need to use ProcessBuilder and one of the redirect methods.
The other alternative is to run the command in a shell. Pass the command as a string, and let the shell take care of the quote handling, substitution of environment variables, globbing, redirection ... and so on.
For example (if you were running on UNIX, Linux or MacOSX):
.exec(new String[]{"/bin/sh", "-c", plpgsql});
For Windows
.exec(new String[]{"cmd.exe", "/C", plpgsql});
Note the "/C" option in the Windows case!
1 - It serves you right for not line-breaking that ~200 character line in your source code! Check out what Java coding standards say about source line lengths ...

CreateProcess error=2 when the path really exists

I'm working with the java ProcessBuilder class to start an instance of nmap on my windows workstation.
The following code produces an exception:
java.io.IOException: Cannot run program "C:\Program Files (x86)\Nmap\nmap.exe -T4 -A -v --max-scan-delay 0ms --min-rate 1000000 --max-retries 0 -oX - 192.168.1.1 ": CreateProcess error=2, The system cannot find the file specified
The value of command is:
C:\Program Files (x86)\Nmap\nmap.exe -T4 -A -v --max-scan-delay 0ms --min-rate 1000000 --max-retries 0 -oX - 192.168.1.1
Running the command is generated right in a command window executes properly.
Any ideas?
String command = this.getCommand().toString();
ExecutionResults results = new ExecutionResults();
ProcessBuilder procBuilder = new ProcessBuilder(new String[]{command.toString()});
try {
Process e = procBuilder.start();
results.setErrors(this.convertStream(e.getErrorStream()));
results.setOutput(this.convertStream(e.getInputStream()));

You're passing the whole command (including parameters) as a single parameter of the ProcessBuilder constructor. It takes a String[], where the first item should be the path to the executable, and the other items should be the parameters. Try
command.split(" ")
instead of
new String[]{command.toString()}
Edit: I see that you have spaces in your path, that will break it :( you could try splitting the executable path and the arguments into two strings. And the constructor argument will be a String[] containing the path itself as the first item and then an array of the parameters split by space.
OR: if you don't mind not using the ProcessBuilder.. this is much simpler:
Process e = Runtime.getRuntime().exec(command);

It is simple from the exception itself,
java.io.IOException: Cannot run program "C:\Program Files (x86)\Nmap\nmap.exe -T4 -A -v --max-scan-delay 0ms --min-rate 1000000 --max-retries 0 -oX - 192.168.1.1 ": CreateProcess error=2, The system
Process builder taking the whole line thinking it is as an executable and trying to run that. Just use the below example,
ProcessBuilder procBuilder = new ProcessBuilder(new String[]{"C:\Program Files (x86)\Nmap\nmap.exe"});
procBuilder.start();
This will work fine. So this is not an issue what you think that java is unable to find the executable. It is taking whole line as an executable. Better you do like below,
ProcessBuilder procBuilder = new ProcessBuilder(new String[]{"C:\Program Files (x86)\Nmap\nmap.exe", "-T4", "-A"}); //add all params
procBuilder.start();
Try this, it should work fine

As the other answers have indicated, your immediate problem is that you're passing an entire command line as if it's the name of a program to run. CreateProcess is looking for a program named "C:\Program Files (x86)\Nmap\nmap.exe -T4 -A etc" and failing to find it.
If you have a string containing a command to run (a program name with arguments, redirection, and so on), then the simplest way to run it is to launch it via the command line processor. Here's a simple example of doing that:
public static void main(String[] args) throws IOException, InterruptedException {
String command = "dir /w";
ProcessBuilder procBuilder = new ProcessBuilder(new String[]{"cmd", "/c", command});
procBuilder.redirectInput(Redirect.INHERIT);
procBuilder.redirectOutput(Redirect.INHERIT);
procBuilder.redirectError(Redirect.INHERIT);
Process p = procBuilder.start();
int ecode = p.waitFor();
System.err.println("Exit code " + ecode);
}

It might be because of a couple of reasons from my experience
Firewall would be removed certain files necessary for the installer. So would suggest to uninstall and reinstall
Can also be because of spaces in the folder path, would suggest to install in new folder which does not have spaces in the path.

run python script inside Java

I need to run a shell command in Windows:
c:\Python27\python.exe c:\probabilistic_cracker\process.py dic2.txt
which is running fine in a command shell.
In Java I do this:
ProcessBuilder pb = new ProcessBuilder(Arrays.asList("c:\\Python27\\python", " c:\\probabilistic_cracker\\process.py"," dic2.txt"));
Process p = pb.start();
or this
ProcessBuilder pb = new ProcessBuilder("c:\\Python27\\python", " c:\\probabilistic_cracker\\process.py"," dic2.txt");
in both cases the result is
c:\Python27\python: can't open file ' c:\probabilistic_cracker\process.py': [Errno 22] Invalid argument

Your command is built correctly but the way you pass it to ProcessBuilder isn't, as stated in its documentation you pass the args directly the way they are, there's no need to add spaces since the ProcessBuilder will take care of that for you.
ProcessBuilder pb = new ProcessBuilder("c:\\Python27\\python", "c:\\probabilistic_cracker\\process.py","dic2.txt");
So just removing those whitespaces you have in the beginning of each argument string will do the trick.

How to use "cd" command using Java runtime?

I've created a standalone java application in which I'm trying to change the directory using the "cd" command in Ubuntu 10.04 terminal. I've used the following code.
String[] command = new String[]{"cd",path};
Process child = Runtime.getRuntime().exec(command, null);
But the above code gives the following error
Exception in thread "main" java.io.IOException: Cannot run program "cd": java.io.IOException: error=2, No such file or directory
Can anyone please tell me how to implement it?

There is no executable called cd, because it can't be implemented in a separate process.
The problem is that each process has its own current working directory and implementing cd as a separate process would only ever change that processes current working directory.
In a Java program you can't change your current working directory and you shouldn't need to. Simply use absolute file paths.
The one case where the current working directory matters is executing an external process (using ProcessBuilder or Runtime.exec()). In those cases you can specify the working directory to use for the newly started process explicitly (ProcessBuilder.directory() and the three-argument Runtime.exec() respectively).
Note: the current working directory can be read from the system property user.dir. You might feel tempted to set that system property. Note that doing so will lead to very bad inconsistencies, because it's not meant to be writable.

See the link below (this explains how to do it):
http://alvinalexander.com/java/edu/pj/pj010016
i.e. :
String[] cmd = { "/bin/sh", "-c", "cd /var; ls -l" };
Process p = Runtime.getRuntime().exec(cmd);

Have you explored this exec command for a java Runtime, Create a file object with the path you want to "cd" to and then input it as a third parameter for the exec method.
public Process exec(String command,
String[] envp,
File dir)
throws IOException
Executes the specified string command in a separate process with the specified environment and working directory.
This is a convenience method. An invocation of the form exec(command, envp, dir) behaves in exactly the same way as the invocation exec(cmdarray, envp, dir), where cmdarray is an array of all the tokens in command.
More precisely, the command string is broken into tokens using a StringTokenizer created by the call new StringTokenizer(command) with no further modification of the character categories. The tokens produced by the tokenizer are then placed in the new string array cmdarray, in the same order.
Parameters:
command - a specified system command.
envp - array of strings, each element of which has environment variable settings in the format name=value, or null if the subprocess should inherit the environment of the current process.
dir - the working directory of the subprocess, or null if the subprocess should inherit the working directory of the current process.
Returns:
A new Process object for managing the subprocess
Throws:
SecurityException - If a security manager exists and its checkExec method doesn't allow creation of the subprocess
IOException - If an I/O error occurs
NullPointerException - If command is null, or one of the elements of envp is null
IllegalArgumentException - If command is empty

This command works just fine
Runtime.getRuntime().exec(sh -c 'cd /path/to/dir && ProgToExecute)

Using one of the process builder's method we could pass the directory where we expect the cmd to be executed. Please see the below example. Also , you can mention the timeout for the process, using wait for method.
ProcessBuilder builder = new ProcessBuilder("cmd.exe", "/c", cmd).directory(new File(path));
Process p = builder.start();
p.waitFor(timeoutSec, TimeUnit.SECONDS);
In the above code, you can pass the file object of the path[where we expect the cmd to be executed] to the directory method of ProcessBuilder

My preferred solution for this is to pass in the directory that the Runtime process will run in. I would create a little method like follows: -
public static String cmd(File dir, String command) {
System.out.println("> " + command); // better to use e.g. Slf4j
System.out.println();
try {
Process p = Runtime.getRuntime().exec(command, null, dir);
String result = IOUtils.toString(p.getInputStream(), Charset.defaultCharset());
String error = IOUtils.toString(p.getErrorStream(), Charset.defaultCharset());
if (error != null && !error.isEmpty()) { // throw exception if error stream
throw new RuntimeException(error);
}
System.out.println(result); // better to use e.g. Slf4j
return result; // return result for optional additional processing
} catch (IOException e) {
throw new RuntimeException(e);
}
}
Note that this uses the Apache Commons IO library i.e. add to pom.xml
<dependency>
<groupId>commons-io</groupId>
<artifactId>commons-io</artifactId>
<version>2.10.0</version>
</dependency>
To use the cmd method e.g.
public static void main(String[] args) throws Exception {
File dir = new File("/Users/bob/code/test-repo");
cmd(dir, "git status");
cmd(dir, "git pull");
}
This will output something like this: -
> git status
On branch main
Your branch is up to date with 'origin/master'.
nothing to commit, working tree clean
> git pull
Already up to date.

Try Use:
Runtime.getRuntime.exec("cmd /c cd path");
This worked
Runtime r = Runtime.getRuntime();
r.exec("cmd /c pdftk C:\\tmp\\trashhtml_to_pdf\\b.pdf C:\\tmp\\trashhtml_to_pdf\\a.pdf cat output C:\\tmp\\trashhtml_to_pdf\\d.pdf");
The below did not work
While using array command did NOT WORK
String[] cmd = {"cmd /c pdftk C:\\tmp\\trashhtml_to_pdf\\b.pdf C:\\tmp\\trashhtml_to_pdf\\a.pdf cat output C:\\tmp\\trashhtml_to_pdf\\d.pdf"}; r.exec(cmd);
FYI am using utility to check OS if its windows above will work for other than windows remove cmd and /c

I had solved this by having the Java application execute a sh script which was in the same directory and then in the sh script had done the "cd".
It was required that I do a "cd" to a specific directory so the target application could work properly.