ProvaPratica 2011.05.30

Link to exam

Esercizio 1

Soluzione di Gab

sender.c

#include <stdlib.h>
#include <stdio.h>
#include <unistd.h>
#include <sys/mman.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <string.h>
#include <signal.h>

#define COMMUNICATION_SIGNAL 25
#define MAXIMUM_LENGTH 4096

#define PID_LENGTH 10


int main(int argc,char *argv[])
{
	int sharedFD = shm_open("/sharedPID", O_CREAT | O_RDWR, S_IRUSR | S_IWUSR);
	if(!sharedFD)
		return;
	ftruncate(sharedFD,sizeof(char)*PID_LENGTH);
	char *sharedVariable = mmap(NULL,sizeof(char)*PID_LENGTH,PROT_READ | PROT_WRITE,MAP_SHARED,sharedFD,0);
	int effectivePID = atoi(sharedVariable);
	int sharedParametersFD = shm_open("/sharedParameters", O_CREAT | O_RDWR, S_IRUSR | S_IWUSR);
	if(!sharedParametersFD)
		return;
	ftruncate(sharedParametersFD,sizeof(char)*MAXIMUM_LENGTH);
	char *parameters = mmap(NULL,sizeof(char)*MAXIMUM_LENGTH,PROT_READ | PROT_WRITE,MAP_SHARED,sharedParametersFD,0);
	char parametersToPass[MAXIMUM_LENGTH];
	int i;
	for(i=0;i<MAXIMUM_LENGTH;i++)
		parametersToPass[i]='\0';
	for(i=0;i<argc;i++)
	{
		strcat(parametersToPass,argv[i]);
		strcat(parametersToPass,"\n");
	}	
	strcpy(parameters,parametersToPass);
	kill(effectivePID,COMMUNICATION_SIGNAL);
	return 0;
}

receiver.c

#include <stdlib.h>
#include <stdio.h>
#include <unistd.h>
#include <sys/mman.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <signal.h>
#include <fcntl.h>
#include <string.h>

#define COMMUNICATION_SIGNAL 25

#define MAXIMUM_LENGTH 4096

#define PID_LENGTH 10



static void signalHandler (int sig, siginfo_t *siginfo, void *context)
{
	int sharedFD = shm_open("/sharedParameters", O_CREAT | O_RDWR, S_IRUSR | S_IWUSR);
	if(!sharedFD)
		return;
	ftruncate(sharedFD,sizeof(char)*MAXIMUM_LENGTH);
	char *parameters = mmap(NULL,sizeof(char)*MAXIMUM_LENGTH,PROT_READ | PROT_WRITE,MAP_SHARED,sharedFD,0);
	printf("Parameters: %s",parameters);
	exit(0);
}


int main(int argc,char *argv[])
{
	int sharedFD = shm_open("/sharedPID", O_CREAT | O_RDWR, S_IRUSR | S_IWUSR);
	if(!sharedFD)
		return;
	char *currentPIDToPass; 	
	asprintf(&currentPIDToPass,"%d",getpid());
	ftruncate(sharedFD,sizeof(char)*PID_LENGTH);
	char *sharedVariable = mmap(NULL,sizeof(char)*PID_LENGTH,PROT_READ | PROT_WRITE,MAP_SHARED,sharedFD,0);
	strcpy(sharedVariable,currentPIDToPass);
	struct sigaction signalStruct;
	signalStruct.sa_sigaction = &signalHandler;
	sigaction(COMMUNICATION_SIGNAL,&signalStruct,NULL);
	while(1){}
	return 0;
}

Gab

Scrivere due programmi in modo che i parametri passati al
primo vengano stampati dal secondo. La comunicazione deve avvenire tramite una shared memory realizzata
con la chiamata POSIX shm_open, la sincronizzazione tramite segnali. Viene attivato per primo il programma
ricevente. (anche i pid dei processi possono venir scambiati attraverso la shared memory!).
Es: scrivere in un terminale:
$./receiver
l'esecuzione di “receiver rimane in attesa”. in un secondo terminale scrivere:
$./sender a bb ccc
nel primo deve comparire
./sender
a
bb
ccc

Soluzione di Dado e Pierg

sender.c

#include <stdio.h>
#include <stdlib.h>
#include <sys/mman.h>
#include <sys/stat.h>
#include <fcntl.h> 

int main(int argc, char * argv[]){
	int fd,i;
	fd=shm_open("/shared",O_RDWR,'w');
	if(fd==-1){
		fprintf(stderr,"Error while opening the shared memory\n");
	}
	for(i=0;i<argc;i++){
		write(fd,argv[i],sizeof(argv[i]));
		write(fd,"\n",1);
	}
	return 0;
}

receiver.c

#include <stdio.h>
#include <stdlib.h>
#include <sys/mman.h>
#include <sys/stat.h>
#include <fcntl.h> 
#define MAXLENGTH 1024

int main(int argc, char * argv[]){
	int fd;
	ssize_t dim;
	char buff[MAXLENGTH];
	fd=shm_open("/shared",O_RDWR,'r');
	while((dim=read(fd,&buff,MAXLENGTH))){
		write(stdout,buff,MAXLENGTH);
	}
	return 0;
}