(Also, see the next iteration.)

I have this small program for terminating processes via their respective process image names (.exe files):

#include <stdio.h>
#include <windows.h>
#include <TlHelp32.h>

int main(int argc, char* argv[]) {
    if (argc != 2) {
        puts("processkiller.exe PROCESS_NAME");
        return EXIT_SUCCESS;

    PROCESSENTRY32 entry;
    entry.dwSize = sizeof(PROCESSENTRY32);
    HANDLE snapshot = CreateToolhelp32Snapshot(TH32CS_SNAPPROCESS, NULL);

    if (Process32First(snapshot, &entry) == TRUE) {
        while (Process32Next(snapshot, &entry) == TRUE) {
            if (strcmp(entry.szExeFile, argv[1]) == 0) {
                HANDLE hProcess = OpenProcess(PROCESS_ALL_ACCESS, 
                TerminateProcess(hProcess, 0);

    return EXIT_SUCCESS;

Note that you need to run processkiller.exe in administrator mode in order to actually terminate the requested processes.

Critique request

Please tell me anything that comes to mind.


1 Answer 1


There is a subtle bug:

Process32First(snapshot, &entry)

already fills entry with the information about the first process in the snapshot. Your code misses that entry because Process32Next() is called immediately. The loop structure should be

if (Process32First(snapshot, &entry) == TRUE) {
    do {
        // ... do something with `entry`...
    } while (Process32Next(snapshot, &entry) == TRUE);

instead. Other things that come into my mind:

  • If the program is called with the wrong number of arguments then the error/usage message should be printed to the standard error and the program should terminate with a non-zero exit code, e.g. EXIT_FAILURE.
  • The return value of CreateToolhelp32Snapshot() is not checked.
  • PROCESS_ALL_ACCESS is not needed in the call to OpenProcess, only PROCESS_TERMINATE.
  • The return values of OpenProcess() and TerminateProcess() are not checked. I would expect a diagnostic message if they fail. In particular, TerminateProcess() and CloseHandle() should only be called if OpenProcess() succeeded.
  • It may be a matter of taste, but == TRUE can be omitted when checking a boolean condition.
  • As a user of this tool I would expect some feedback to see if a matching process was found, and how many processes were killed.
  • \$\begingroup\$ Thanks for debugging the loop! Nice answer! \$\endgroup\$
    – coderodde
    Aug 21, 2020 at 9:00

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