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#include <stdio.h>
#include <unistd.h>
#include <sys/wait.h>
#include <stdlib.h>
#include "/usr/include/linux/limits.h"
void decremente (int a,int n)
{
int pid,reason;
int tubes[n][2];
int resultat;
int termine=0;
int new_value=a;
int cpt=0;
int lec,ecr;
for (int j=0;j<n;j++){
if(pipe(tubes[j]) == -1)
perror("pipe");
}
write(tubes[0][1],&a,sizeof(int));
for(int i=0;i<n;i++){
switch(pid=fork()){
case -1:
perror("fork");
break;
case 0:
lec=tubes[i][0];
ecr=tubes[(i+1)%n][1];
if(read(lec,&new_value,sizeof(int)) == -1)
perror("read");
printf("%d\n",new_value);
close(lec);
new_value--;
if(new_value == 0){
exit(i);
} else {
if(write(ecr,&new_value,sizeof(int)) == -1)
perror("write");
}
close (ecr);
break;
default:
break;
}
}
if(termine == 1){
for(cpt=0;cpt<n;cpt++){
if(wait(&reason)==-1)
perror("wait");
}
}
fprintf(stdout, "RESULTAT : %d\n",resultat);
}
int main (int argc, char**argv)
{
if(argc != 3)
perror("Usage : ./exec <a> <n>");
decremente(atoi(argv[1]),atoi(argv[2]));
return 0;
} |
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