int main(int argc, char *argv[])
{
pid_t child1, child2;
if (argc < 3) {
printf("Usage: waitpid [0 1] [0 1]\n");
exit(1);
}
child1 = fork();
if (child1 < 0) {
die("child1 fork");
}
else if (child1 == 0) {
child2 = fork();
if (child2 < 0) {
die("child2 fork");
}
else if (child2 == 0) {
child2_do();
}
else {
child1_do(child2, argv[1]);
}
}
else {
father_do(child1, argv[2]);
}
return 0;
}
int main(int argc,char *argv[])
{
int pid1, pid2;
// fd[0] for read, fd[1] for write
int fd[2];
pipe(fd);
// 1-->2
switch(pid1 = fork())
{
case -1:
{
printf("fork error\n");
exit(1);
}
case 0:
{
close(fd[1]);
child_1_do(fd[0]);
}
default:
{
printf("1 --> 2, 1 id=%d, 2 id=%d\n", getpid(), pid1);
// 1 --> 3
switch (pid2 = fork())
{
case -1:
{
printf("fork error\n");
exit(1);
}
case 0:
{
close(fd[1]);
child_2_do(fd[0]);
}
default:
printf("1 --> 3, 1 id=%d, 3 id=%d\n", getpid(), pid2);
break;
}
break;
}
}
close(fd[0]);
father_do(pid1, pid2, fd[1]);
return 0;
}
