A simple C WinAPI program for terminating processes via process image names

Question

(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, 
                                              FALSE, 
                                              entry.th32ProcessID);
                TerminateProcess(hProcess, 0);
                CloseHandle(hProcess);
            }
        }
    }

    CloseHandle(snapshot);
    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.

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.