我希望我的父进程等待所有子进程完成再继续,我有一个解决方案。
int status;
pid_t pid = 0;
int num = 0;
for (int i = 0; i < NUMBER_OF_PROCESSES; i++)
{
pid = fork();
if (pid == 0)
{
//printf("Hello from Childn");
sleep(5 - i);
printf("Hello from Child %dn",i + 1);
num++;
return 0;
}
else if (pid)
{
waitpid(pid, &status, 0);
continue;
}
else
{
printf("Errorn");
exit(1);
}
}
printf("Hello from the process, currentPid : %d, pid : %dn", getpid(), pid);
return 0;
但是似乎我必须等待每个子进程才能完成,有没有办法使所有子进程都必须能够并行运行?
您只需要在循环中启动进程,然后在原始进程中循环等待,直到没有更多的活着的孩子。喜欢这个:
for (int i = 0; i < NUMBER_OF_PROCESSES; i++) {
pid = fork();
if (pid == 0) { // child
sleep(5 - i);
printf("Hello from Child %dn",i + 1);
num++;
return 0;
}
else if (pid==-1) {
printf("Errorn");
break; // out on failure
}
}
// try to wait for any children while there exists at least one
while ((pid=waitpid(-1,&status,0))!=-1) {
printf("Process %d terminatedn",pid);
}
因此,孩子将同时生活,父母将等待他们的终止。
您可以启动所有子项(并保留其 pid),然后,您将在循环中使用 waitpid(请参阅等待任何子项的选项),直到没有子项。
听起来对你来说很好吗?
编辑:
#define NB_PROCESSES 5
int main(void)
{
pid_t pidChild[NB_PROCESSES];
pid_t stoppedChild;
int nbChild = 0;
printf("Launching all child.n");
for (int i = 0; i < NB_PROCESSES; ++i) {
if ((pidChild[i] = fork()) == -1) {
printf("Error while fork the %d child : errno = '%s'.n", i, strerror(errno));
} else {
if (pidChild[i] == 0) {
sleep(NB_PROCESSES - i);
printf("Hello from Child %dn",i);
return (0);
} else {
++nbChild;
}
}
}
printf("Waiting all child.n");
while (nbChild) {
stoppedChild = waitpid(WAIT_ANY, NULL, 0);
for (int i = 0; i < NB_PROCESSES; ++i) {
if (stoppedChild == pidChild[i]) {
printf("Child %d stopped.n", i);
}
}
--nbChild;
}
printf("Hello from the process, currentPid : %dn", getpid());
return (0);
}
你可以像这样保留他们的pid。
使用 waitpid
waitpid(childPid, &returnStatus, 0); // Parent process waits here for child to terminate.
if (returnStatus == 0) // Verify child process terminated without error.
{
std::cout << "The child process terminated normally." << std::endl;
}
if (returnStatus == 1)
{
std::cout << "The child process terminated with an error!." << std::endl;
}
并行的子进程。一个子项可能会快速运行并在下一个运行之前终止,在这种情况下,子项实际上是串行运行的。
for( int n = 0; n < 4; ++n ) {
switch( fork()) {
/* do stuff, but don't wait() or terminate */
}
}