Develop Reference

Hide "Python" on Task Manager

I have python program and this is compiled file(.pyc)
I wrote Launcher with C#. This launcher starts this Python program (pyc file).
But as you see in picture, my python program's top name is "Python", how can i hide this Python?
Thanks.
C# Launch python code:
private bool ProcessCalistir(string path, string Args = "", bool wait = false)
{
Process proc = new Process();
//proc.StartInfo.WorkingDirectory = PythonKlasor;
proc.StartInfo.WorkingDirectory = AppDomain.CurrentDomain.BaseDirectory;
proc.StartInfo.FileName = path;
proc.StartInfo.Arguments = Args;
proc.StartInfo.UseShellExecute = false;
proc.StartInfo.CreateNoWindow = true;
proc.StartInfo.Verb = "runas";
proc.Start();
if (wait) proc.WaitForExit();
return true;
}
ProcessCalistir("python.exe", "MyPythonProgram.pyc");

How can I make a linux background process (in c) that launches a Python script

I made a Linux background process (in c++) that monitors a directory and attempts to launch a Python script if a certain file appears in that directory. My issue is that the child process responsible for launching the Python script exits immediately after the execvp function is called and I can't understand why. All of the necessary files are under root's ownership. Here is my code if it helps. Thank you in advance for any pointers! I have marked the error in my code where the error occurs. I have also included the Python script to be called
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/wait.h>
#include <stdlib.h>
#include <unistd.h>
#include <stdio.h>
using namespace std;
char* arguments[3];
FILE* fd;
const char* logFilePath = "/home/BluetoothProject/Logs/fileMonitorLogs.txt";
char* rfcommPath = (char*)"/home/BluetoothProject/RFCOMMOut.py";
void logToFile(const char*);
void doWork();
void logToFile(const char* str) {
fd = fopen(logFilePath, "a");
fprintf(fd, "%s\n", str);
fclose(fd);
}
int main() {
arguments[0] = (char*)"python";
arguments[1] = rfcommPath;
arguments[2] = NULL;
pid_t pid = fork();
if(pid < 0) {
printf("Fork failed");
exit(1);
} else if(pid > 0) {
exit(EXIT_SUCCESS);
}
umask(0);
pid_t sid = setsid();
if(sid < 0) {
logToFile("setsid() didn't work.");
exit(1);
}
if ((chdir("/")) < 0) {
logToFile("chdir() didn't work.");
exit(EXIT_FAILURE);
}
close(STDIN_FILENO);
close(STDOUT_FILENO);
close(STDERR_FILENO);
doWork();
}
void doWork() {
pid_t pid = fork();
if(pid < 0) {
logToFile("doWork() fork didn't work.");
} else if(pid > 0) {
int status = 0;
waitpid(pid, &status, 0);
if(WEXITSTATUS(status) == 1) {
logToFile("Child process exited with an error.");
}
} else {
int error = execvp(arguments[0], arguments); //Here is where the error is
if(error == -1) {
logToFile("execvp() failed.");
}
exit(1);
}
}
Python script (AKA RFCOMMOut.py)
import RPi.GPIO as gpio
import serial
led_state = 0
led_pin = 11
gpio.setmode(gpio.BOARD)
gpio.setwarnings(False)
gpio.setup(led_pin, gpio.OUT)
try:
ser = serial.Serial(port = '/dev/rfcomm0',
baudrate = 9600,
parity = serial.PARITY_NONE,
stopbits = serial.STOPBITS_ONE,
bytesize = serial.EIGHTBITS)
except IOException as e:
logFile = open("/home/BluetoothProject/Logs/fileMonitorLogs.txt", "a")
logFile.write("(First error handler) There was an exception:\n")
logFile.write(str(e))
logFile.write("\n")
logFile.close()
#gpio.output
def process_input(input):
global led_state
if input == "I have been sent.\n":
if led_state == 1:
led_state = 0
gpio.output(led_pin, led_state)
else:
led_state = 1
gpio.output(led_pin, led_state)
while True:
try:
transmission = ser.readline()
process_input(transmission)
except IOError as e:
logFile = open("/home/BluetoothProject/Logs/fileMonitorLogs.txt", "a")
logFile.write("(second error handler) There was an exception:\n")
logFile.write(str(e))
logFile.write("\n")
logFile.close()
break
led_state = 0
gpio.output(led_pin, led_state)
gpio.cleanup()
print("End of program\n")

The question is a little unclear, so I'll try to take a few different educated guesses at what the problem is and address each one individually.
TL;DR: Remove close(STDOUT_FILENO) and close(STDERR_FILENO) to get more debugging information which will hopefully point you in the right direction.
execvp(3) is returning -1
According to the execvp(3) documentation, execvp(3) sets errno when it fails. In order to understand why it is failing, your program will need to output the value of errno somewhere; perhaps stdout, stderr, or your log file. A convenient way to do this is to use perror(3). For example:
#include <stdio.h>
...
void doWork() {
...
} else {
int error = execvp(arguments[0], arguments);
if(error == -1) {
perror("execvp() failed");
}
}
...
}
Without knowing what that errno value is, it will be difficult to identify why execvp(3) is failing.
execvp(3) is succeeding, but my Python program doesn't appear run
execvp(3) succeeding means that the Python interpreter has successfully been invoked (assuming that there is no program in your PATH that is named "python", but is not actually a Python interpreter). If your program doesn't appear to be running, that means Python is having difficulty loading your program. To my knowledge, Python will always output relevant error messages in this situation to stderr; for example, if Python cannot find your program, it will output "No such file or directory" to stderr.
However, it looks like your C program is calling close(STDERR_FILENO) before calling doWork(). According to fork(2), child processes inherit copies of their parent's set of open file descriptors. This means that calling close(STDERR_FILENO) before forking will result in the child process not having an open stderr file descriptor. If Python is having any errors executing your program, you'll never know, since Python is trying to notify you through a file descriptor that doesn't exist. If execvp(3) is succeeding and the Python program appears to not run at all, then I recommend you remove close(STDERR_FILENO) from your C program and run everything again. Without seeing the error message output by Python, it will be difficult to identify why it is failing to run the Python program.
As an aside, I recommend against explicitly closing stdin, stdout, and stderr. According to stdin(3), the standard streams are closed by a call to exit(3) and by normal program termination.
execvp(3) is succeeding, my Python program is running, but my Python program exits before it does any useful work
In this case, I'm not sure what the problem might be, since I'm not very familiar with Raspberry Pi. But I think you'll have an easier time debugging if you don't close the standard streams before running the Python program.
Hope this helps.

How to execute a pyomo model script inside Spring?

I have a web interface built with Spring and I want to execute the command "python file.py" from it.
The main problem is that inside the file.py there is a pyomo model that is supposed to give some output. I can execute a python script if it's a simple print or something, but the pyomo model is completely ignored.
What could be the reason?
Here is the code I wrote in the controller to execute the call:
#PostMapping("/execute")
public void execute(#ModelAttribute("component") #Valid Component component, BindingResult result, Model model) {
Process process = null;
//System.out.println("starting!");
try {
process = Runtime.getRuntime().exec("python /home/chiara/Documents/GitHub/Pyomo/Solver/test/sample.py");
//System.out.println("here!");
} catch (Exception e) {
System.out.println("Exception Raised" + e.toString());
}
InputStream stdout = process.getInputStream();
BufferedReader reader = new BufferedReader(new InputStreamReader(stdout, StandardCharsets.UTF_8));
String line;
try {
while ((line = reader.readLine()) != null) {
System.out.println("stdout: " + line);
}
} catch (IOException e) {
System.out.println("Exception in reading output" + e.toString());
}
}

Update: I found that what I was missing was that I didn't check where the code run. So be sure to do so and eventually move the input files (if you have any) in the directory where python is executing, otherwise the script can't find them and elaborate them.
You can use
cwd = os.getcwd()
to check the current working directory of a process.
Another possibility is to redirect the stderr on the terminal or in a log file, because from the Server terminal you won't see anything even if there are errors.
The code posted in the question is the correct way to invoke a bash command from java.

Node.js child process to Python process

I must send text from a node.js child process to a python process.
My dummy node client looks like
var resolve = require('path').resolve;
var spawn = require('child_process').spawn;
data = "lorem ipsum"
var child = spawn('master.py', []);
var res = '';
child.stdout.on('data', function (_data) {
try {
var data = Buffer.from(_data, 'utf-8').toString();
res += data;
} catch (error) {
console.error(error);
}
});
child.stdout.on('exit', function (_) {
console.log("EXIT:", res);
});
child.stdout.on('end', function (_) {
console.log("END:", res);
});
child.on('error', function (error) {
console.error(error);
});
child.stdout.pipe(process.stdout);
child.stdin.setEncoding('utf-8');
child.stdin.write(data + '\r\n');
while the Python process master.py is
#!/usr/bin/env python
import sys
import codecs
if sys.version_info[0] >= 3:
ifp = codecs.getreader('utf8')(sys.stdin.buffer)
else:
ifp = codecs.getreader('utf8')(sys.stdin)
if sys.version_info[0] >= 3:
ofp = codecs.getwriter('utf8')(sys.stdout.buffer)
else:
ofp = codecs.getwriter('utf8')(sys.stdout)
for line in ifp:
tline = "<<<<<" + line + ">>>>>"
ofp.write(tline)
# close files
ifp.close()
ofp.close()
I must use a utf-8 encoded input reader so I'm using a sys.stdin, but it seems that when node.js writes to child process stdin using child.stdin.write(data + '\r\n');, this will not be read by sys.stdin in for line in ifp:

You'll need to call child.stdin.end() in the Node program after the final call to child.stdin.write(). Until end() is called, the child.stdin writable stream will hold the written data in a buffer, so the Python program won't see it. See the Buffering discussion in https://nodejs.org/docs/latest-v8.x/api/stream.html#stream_buffering for details.
(If you write lots of data into stdin then the write buffer will eventually fill to a point where the accumulated data will be flushed out automatically to the Python program. The buffer will then begin again to collect data. An end() call is needed to make sure that the final portion of the written data is flushed out. It also has the effect of indicating to the child process that no more data will be sent on this stream.)

NSTask requires flush when reading from a process' stdout, Terminal does not

I have a simple Python script that asks for your name, then spits it back out:
def main():
print('Enter your name: ')
for line in sys.stdin:
print 'You entered: ' + line
Pretty simple stuff! When running this in the OS X Terminal, it works great:
$ python nameTest.py
Enter your name:
Craig^D
You entered: Craig
But, when attempting to run this process via an NSTask, the stdout only appears if additional flush() calls are added to the Python script.
This is how I have my NSTask and piping configured:
NSTask *_currentTask = [[NSTask alloc] init];
_currentTask.launchPath = #"/usr/bin/python";
_currentTask.arguments = [NSArray arrayWithObject:#"nameTest.py"];
NSPipe *pipe = [[NSPipe alloc] init];
_currentTask.standardOutput = pipe;
_currentTask.standardError = pipe;
dispatch_queue_t stdout_queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_BACKGROUND, 0);
__block dispatch_block_t checkBlock;
checkBlock = ^{
NSData *readData = [[pipe fileHandleForReading] availableData];
NSString *consoleOutput = [[NSString alloc] initWithData:readData encoding:NSUTF8StringEncoding];
dispatch_sync(dispatch_get_main_queue(), ^{
[self.consoleView appendString:consoleOutput];
});
if ([_currentTask isRunning]) {
[NSThread sleepForTimeInterval:0.1];
checkBlock();
} else {
dispatch_sync(dispatch_get_main_queue(), ^{
NSData *readData = [[pipe fileHandleForReading] readDataToEndOfFile];
NSString *consoleOutput = [[NSString alloc] initWithData:readData encoding:NSUTF8StringEncoding];
[self.consoleView appendString:consoleOutput];
});
}
};
dispatch_async(stdout_queue, checkBlock);
[_currentTask launch];
But when running the NSTask, this is how it appears (it is initially blank, but after entering my name and pressing CTRL+D, it finishes all at once):
Craig^DEnter your name:
You entered: Craig
So, my question is: How can I read the stdout from my NSTask without requiring the additional flush() statements in my Python script? Why does the Enter your name: prompt not appear immediately when run as an NSTask?

When Python sees that its standard output is a terminal, it arranges to automatically flush sys.stdout when the script reads from sys.stdin. When you run the script using NSTask, the script's standard output is a pipe, not a terminal.
UPDATE
There is a Python-specific solution to this. You can pass the -u flag to the Python interpreter (e.g. _currentTask.arguments = #[ #"-u", #"nameTest.py"];), which tells Python not to buffer standard input, standard output, or standard error at all. You can also set PYTHONUNBUFFERED=1 in the process's environment to achieve the same effect.
ORIGINAL
A more general solution that applies to any program uses what's called a “pseudo-terminal” (or, historically, a “pseudo-teletype”), which we shorten to just “pty”. (In fact, this is what the Terminal app itself does. It is a rare Mac that has a physical terminal or teletype connected to a serial port!)
Each pty is actually a pair of virtual devices: a slave device and a master device. The bytes you write to the master, you can read from the slave, and vice versa. So these devices are more like sockets (which are bidirectional) than like pipes (which are one-directional). In addition, a pty also let you set terminal I/O flags (or “termios”) that control whether the slave echoes its input, whether it passes on its input a line at a time or a character at a time, and more.
Anyway, you can open a master/slave pair easily with the openpty function. Here's a little category that you can use to make an NSTask object use the slave side for the task's standard input and output.
NSTask+PTY.h
#interface NSTask (PTY)
- (NSFileHandle *)masterSideOfPTYOrError:(NSError **)error;
#end
NSTask+PTY.m
#import "NSTask+PTY.h"
#import <util.h>
#implementation NSTask (PTY)
- (NSFileHandle *)masterSideOfPTYOrError:(NSError *__autoreleasing *)error {
int fdMaster, fdSlave;
int rc = openpty(&fdMaster, &fdSlave, NULL, NULL, NULL);
if (rc != 0) {
if (error) {
*error = [NSError errorWithDomain:NSPOSIXErrorDomain code:errno userInfo:nil];
}
return NULL;
}
fcntl(fdMaster, F_SETFD, FD_CLOEXEC);
fcntl(fdSlave, F_SETFD, FD_CLOEXEC);
NSFileHandle *masterHandle = [[NSFileHandle alloc] initWithFileDescriptor:fdMaster closeOnDealloc:YES];
NSFileHandle *slaveHandle = [[NSFileHandle alloc] initWithFileDescriptor:fdSlave closeOnDealloc:YES];
self.standardInput = slaveHandle;
self.standardOutput = slaveHandle;
return masterHandle;
}
#end
You can use it like this:
NSTask *_currentTask = [[NSTask alloc] init];
_currentTask.launchPath = #"/usr/bin/python";
_currentTask.arguments = #[[[NSBundle mainBundle] pathForResource:#"nameTest" ofType:#"py"]];
NSError *error;
NSFileHandle *masterHandle = [_currentTask masterSideOfPTYOrError:&error];
if (!masterHandle) {
NSLog(#"error: could not set up PTY for task: %#", error);
return;
}
Then you can read from the task and write to the task using masterHandle.