Traversing the Thread List

The following example obtains a list of running threads for the specified process. First, the RefreshThreadList function takes a snapshot of the currently executing threads in the system using the CreateToolhelp32Snapshot function, then it walks through the list recorded in the snapshot, using the Thread32First and Thread32Next functions. The parameter for RefreshThreadList is the identifier of the process whose threads will be listed.

#include <windows.h>
#include <tlhelp32.h>
#include <stdio.h>

BOOL RefreshThreadList (DWORD dwOwnerPID) 
{ 
    HANDLE        hThreadSnap = NULL; 
    BOOL          bRet        = FALSE; 
    THREADENTRY32 te32        = {0}; 
 
    // Take a snapshot of all threads currently in the system. 

    hThreadSnap = CreateToolhelp32Snapshot(TH32CS_SNAPTHREAD, 0); 
    if (hThreadSnap == (HANDLE)-1) 
        return (FALSE); 
 
    // Fill in the size of the structure before using it. 

    te32.dwSize = sizeof(THREADENTRY32); 
 
    // Walk the thread snapshot to find all threads of the process. 
    // If the thread belongs to the process, add its information 
    // to the display list.
 
    if (Thread32First(hThreadSnap, &te32)) 
    { 
        do 
        { 
            if (te32.th32OwnerProcessID == dwOwnerPID) 
            { 
                printf( "\nTID\t\t%d\n", te32.th32ThreadID); 
                printf( "Owner PID\t%d\n", te32.th32OwnerProcessID); 
                printf( "Delta Priority\t%d\n", te32.tpDeltaPri); 
                printf( "Base Priority\t%d\n", te32.tpBasePri); 
            } 
        } 
        while (Thread32Next(hThreadSnap, &te32)); 
        bRet = TRUE; 
    } 
    else 
        bRet = FALSE;          // could not walk the list of threads 
 
    // Do not forget to clean up the snapshot object. 

    CloseHandle (hThreadSnap); 
 
    return (bRet); 
}