Semkill.c

Für das Entfernen von verwaisten Semaphoren :

C-Code zum Download : semkill.c

Source :

#include <sys/types.h>
#include <sys/ipc.h>
#include <sys/sem.h>
#include <stdlib.h>
#include <stdio.h>
#include <errno.h>
#include <dirent.h>

// #define DEBUG

void usage(const char *progname)
{
        fprintf(stdout, "nusage: %s <semid>nn", progname);
}

int main(int argc, char **argv)
{
        int semid, pid;
        int count;

        if ( argc != 2 )
        {
                usage(argv[0]);
                exit(EXIT_FAILURE);
        }


#ifdef DEBUG
        fprintf(stdout, "argv[1] = >>%s<<n", argv[1]);
#endif

        semid = atoi(argv[1]);


#ifdef DEBUG
        fprintf(stdout, "argv[1] nach atoi: %dn", semid);
#endif

        if ( semid < 1 )
        {
                fprintf(stderr, "Ungültige semid: %dn", semid);
                exit(EXIT_FAILURE);
        }

        pid = semctl(semid, 0, GETPID, NULL);
        if ( pid < 0 )
        {
                perror("semctl");
                exit(EXIT_FAILURE);

        count = semctl(semid, 0, GETNCNT, NULL);
        if ( count < 0 )
        {
                perror("semctl");
                exit(EXIT_FAILURE);
        }

        if ( count == 0 )
        {
                // Kein Prozess mehr vorhanden? Semaphore löschen...
                if ( pid == 0 )
                {
                        int rc = semctl(semid, 0, IPC_RMID, NULL);
                        if ( rc < 0 )
                        {
                                perror("semctl");
                                exit(EXIT_FAILURE);
                        }
                        fprintf(stdout, "Semaphore %d gelöscht.n", semid);
                }
                else    // PID noch gesetzt
                {
                        DIR *proc_pid = NULL;
                        char pid_pfad[48];

                        // Pfad zusammenbauen
                        snprintf(pid_pfad, sizeof(pid_pfad), "/proc/%d",
pid);

                        // Ist der Besitzer-Prozess noch am Leben?
                        proc_pid = opendir(pid_pfad);
                        if ( proc_pid == NULL )
                        {
                                // Prozess nicht mehr vorhanden
                                if ( errno == ENOENT )
                                {
                                        // Semaphore löschen
                                        int rc = semctl(semid, 0, IPC_RMID,
NULL);
                                        if ( rc < 0 )
                                        {
                                                perror("semctl");
                                                exit(EXIT_FAILURE);
                                        }
                                        fprintf(stdout, "PID %d has tits up,
Semaphore %d gelöscht.n", pid, semid);
                                }
                        }
                        else    // Prozess lebt noch
                        {
                                closedir(proc_pid);
#ifdef DEBUG
                                fprintf(stdout, "Semaphore in Benutzung: PID =
%d; Count = %dn", pid, count);
#endif
                        }
                }
        }
        else    // count > 0
        {
#ifdef DEBUG
                fprintf(stdout, "Semaphore in Benutzung: PID = %d; Count =
%dn", pid, count);
#endif
        }

        exit(EXIT_SUCCESS);
}