#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/stat.h>
#include <sys/sem.h>
#include <sys/wait.h>
int main( void )
{
int status;
key_t semkey; //... zmienne opisujące
int nsems,semflag,semid; // tworzoną tablicę semaforów
struct sembuf sems; //... struktura dla semop()
nsems = 1; //... tworzymy tablicę semaforów, z jednym semaforem
semkey = ftok( "/tmp",'k'+'m' );
semflag = IPC_CREAT | S_IRUSR | S_IWUSR;
semid = semget( semkey,nsems,semflag );
sems.sem_num = 0; //... indeks do semafora, pierwszy=0 !
sems.sem_op = 7; //... może współdzielić 7 procesów
sems.sem_flg = 0x0; //... czyli z blokadą
semop( semid,&sems,nsems ); //... inicjujemy semafor
//... teraz pozostaje już tylko utworzyć proces potomny
switch( fork() )
{
case -1: //... obsługa błędu fork()
printf( "!.!.!... błąd fork()...!.!.!\n" ); exit( 1 ); break;
case 0: //... kod dla procesu potomnego
printf( "[%u] semval=%d\n",(unsigned)getpid(),
semctl( semid,0,GETVAL ) ); exit( 0 ); break;
default: //...kod dla procesu nadrzędnego
wait( &status );
printf( "[%u] semval=%d\n",(unsigned)getpid(),
semctl( semid,0,GETVAL ) );
semctl( semid,0x0,IPC_RMID); //... usuwamy semafory
}
return 0;
}
Replies to Re: Re: Re: Re: Re: Re: Re: ss
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