ProvaPratica 2011.05.30
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Esercizio 1
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 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(¤tPIDToPass,"%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
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;
}
Manca la sincronizzazione tramite segnali --FedericoB (talk) 16:33, 27 May 2017 (CEST)
Soluzione di FedericoB
receiver
#define _GNU_SOURCE
#include <stdlib.h>
#include <stdio.h>
#include <unistd.h>
#include <sys/mman.h>
#include <sys/stat.h>
#include <signal.h>
#include <fcntl.h>
#include <string.h>
#define MAXSIZE 4096
int main(int argc, char* argv[]) {
int sharedFD;
printf("pid = %d\n", getpid());
//create shared memory object
if ((sharedFD = shm_open("/sharedPID", O_CREAT | O_RDWR, S_IRUSR | S_IWUSR)) != -1) {
//set size of shared memory object
if (ftruncate(sharedFD, MAXSIZE) == 0) {
//create a memory mapping with sharedVariable and the shared memory object
#define OFFSET 0
#define ADDRESS NULL
char* sharedVariable = mmap(ADDRESS, MAXSIZE, PROT_READ | PROT_WRITE, MAP_SHARED, sharedFD, OFFSET);
if (sharedVariable != MAP_FAILED) {
sprintf(sharedVariable, "%d\n", getpid());
sigset_t mask;
//initialize signal mask
sigemptyset(&mask);
sigaddset(&mask, SIGUSR1);
//block default handler for SIGUSR1
sigprocmask(SIG_BLOCK, &mask, NULL);
int sig;
//wait for a SIGURS1
sigwait(&mask, &sig);
printf("%s\n", sharedVariable);
shm_unlink("/sharedPID");
return 0;
} else {
perror(NULL);
}
} else {
perror(NULL);
}
} else {
perror(NULL);
}
}
sender
#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 MAXSIZE 4096
int main(int argc,char *argv[]) {
int sharedFD;
//create shared memory object
if ((sharedFD = shm_open("/sharedPID", O_CREAT | O_RDWR, S_IRUSR | S_IWUSR)) != -1) {
ftruncate(sharedFD, MAXSIZE);
#define OFFSET 0
#define ADDRESS NULL
char* sharedVariable = mmap(ADDRESS, MAXSIZE, PROT_READ | PROT_WRITE, MAP_SHARED, sharedFD, OFFSET);
int effectivePID = atoi(sharedVariable);
printf("pid = %d\n",effectivePID);
shm_unlink("/sharedPID");
int i;
for (i=0;i<MAXSIZE;i++) sharedVariable[i]='\0';
for (i = 1; i < argc; i++) {
strcat(sharedVariable, argv[i]);
strcat(sharedVariable, " ");
}
kill(effectivePID, SIGUSR1);
return 0;
} else {
perror(NULL);
}
}