Checking If Process Still Running

How to check if a process id (PID) exists

To check for the existence of a process, use

kill -0 $pid

But just as @unwind said, if you want it to terminate in any case, then just

kill $pid

Otherwise you will have a race condition, where the process might have disappeared after the first kill -0.

If you want to ignore the text output of kill and do something based on the exit code, you can

if ! kill $pid > /dev/null 2>&1; then
    echo "Could not send SIGTERM to process $pid" >&2
fi

Checking if a Process is Currently running by name in rust

You can use sysinfo crate, or particularly processes_by_name

You can get iterator to processes containing the name using the function

fn processes_by_name<'a>(&'a self, name: &'a str) -> Box<dyn Iterator<Item = &'a Process> + 'a>

You can use it like this

use sysinfo::{ProcessExt, System, SystemExt};

let s = System::new_all();
for process in s.processes_by_name("htop") {
    //check here if this is your process
}

UPDATE: New version (0.23.0) also contains processes_by_exact_name

It returns an iterator to processes with the exact given name
You can use it like this

use sysinfo::{ProcessExt, System, SystemExt};

let s = System::new_all();
for process in s.processes_by_exact_name("htop") {
    //Your code goes here
}

How to Correctly Check if a Process is running and Stop it

The way you're doing it you're querying for the process twice. Also Lynn raises a good point about being nice first. I'd probably try something like the following:

# get Firefox process
$firefox = Get-Process firefox -ErrorAction SilentlyContinue
if ($firefox) {
  # try gracefully first
  $firefox.CloseMainWindow()
  # kill after five seconds
  Sleep 5
  if (!$firefox.HasExited) {
    $firefox | Stop-Process -Force
  }
}
Remove-Variable firefox

check if process is running with only Path provided

You can filter by Path and select Id:

Get-Process | Where-Object {$_.Path -EQ "C:\Users\Administrator\Desktop\1\hello.exe"} | Select-Object Id

By the way:

Get-Process sadly does not even shows you the path to the process.

It does, if you ask it to (it returns an object like all those commands do, and it has a default selection of properties to list but that doesn't mean you can't access the remaining properties by specifically selecting them):

Get-Process explorer | Select-Object Path

(or use Select-Object * to see all available properties)

It appears you haven't yet understood how PowerShell objects work, so I'd recommend you to check out some tutorials about this topic, for instance this article about selecting and filtering and this one that goes more into detail about the filtering options.

How to check if a process is running on Windows?

There is no direct way to query general processes as each OS handles them differently.

You kinda stuck with using proxies such as direct OS commands...

You can however, find a specific process using tasklist.exe with /fi parameter.

e.g: tasklist.exe /nh /fi "Imagename eq chrome.exe"
Note the mandatory double quotes.

Syntax & usage are available on MS Technet site.

Same example, filtering for "chrome.exe" in Java:

String findProcess = "chrome.exe";
String filenameFilter = "/nh /fi \"Imagename eq "+findProcess+"\"";
String tasksCmd = System.getenv("windir") +"/system32/tasklist.exe "+filenameFilter;

Process p = Runtime.getRuntime().exec(tasksCmd);
BufferedReader input = new BufferedReader(new InputStreamReader(p.getInputStream()));

ArrayList<String> procs = new ArrayList<String>();
String line = null;
while ((line = input.readLine()) != null) 
    procs.add(line);

input.close();

Boolean processFound = procs.stream().filter(row -> row.indexOf(findProcess) > -1).count() > 0;
// Head-up! If no processes were found - we still get: 
// "INFO: No tasks are running which match the specified criteria."

How to check if a given process is running when having its handle

Call WaitForSingleObject on that handle, and use a timeout parameter of zero. If the process is still running, the function will return Wait_Timeout; if the process has terminated, then it will return Wait_Object_0 (because process termination causes its handles to become signaled.)

If you want to know what the exit status of the process is, then call GetExitCodeProcess.

How can I know if a process is running?

This is a way to do it with the name:

Process[] pname = Process.GetProcessesByName("notepad");
if (pname.Length == 0)
  MessageBox.Show("nothing");
else
  MessageBox.Show("run");

You can loop all process to get the ID for later manipulation:

Process[] processlist = Process.GetProcesses();
foreach(Process theprocess in processlist){
   Console.WriteLine("Process: {0} ID: {1}", theprocess.ProcessName, theprocess.Id);
}

Judging if a process exists by pid windows

Would there be a better method on approaching this type of problem?

Indeed so.

Using PID for checking if process is alive is not a solution - so you should go back and check your overall design.

Just use the handle you get when the process is started:

HANDLE hProcess = CreateProcess(...

It could sound like the process is not created from this process - so perhaps obtain it like you do once, and keep it (ie. try to store the handle once the process is found instead of keep using the PID).

Now you can check using for example the function GetExitCodeProcess ala.:

  DWORD returnCode{};
  if (GetExitCodeProcess(handle, &returnCode)) {
    if (returnCode != STILL_ACTIVE) {
      //no longer active

The reason using PID is bad is twofold: the OS may keep the process in a dead state for a while and the PID may already be reused for a new process once you check it (you simply cannot control that in any normal cases).

As for the ERROR_ACCESS_DENIED: it's not a reliable method at all to check if the process exists or not.

Detecting if a process is still running

You can test the process life by using

bool isProcessRunning(HANDLE process)
{
   return WaitForSingleObject( process, 0 ) == WAIT_TIMEOUT;
}