有人可以帮助我，不一定完成我的作业。
我需要使用fork（）创建一个进程树;在Unix / C中，到目前为止，我能够达到第4级的最好是我的代码：
/* Includes */
#include <unistd.h> /* Symbolic Constants */
#include <stdio.h> /* Input/Output */
#include <stdlib.h> /* General Utilities */
int main()
{
pid_t childpid;
pid_t pid;
int i;
childpid=fork();
waitpid();
i=0;
for (; i<1; i++) {
int b=0;
for (; b<1;b++) {
childpid=fork();
fprintf(stderr,"the value of i is %d, i am %ld , my parent is %ld\n",
i, (long)getpid(), (long)getppid());
if (childpid==0) {
break;
}
}
if (childpid==0) {
break;
}
}
sleep(1);
}
我对C编程非常陌生，总体来说编程很好，所以我想向公众询问我缺少哪些步骤。树深度需要由用户指定，所以我想我会使用n a for循环，但只能在一个级别上相乘而不是创建新级别。
有人可以帮助我，并指出我正确的方向:) 我需要它像这样分叉
i
/ \
/ \
/ \
/ \
/ \
i i
/ \ / \
/ \ / \
i i i i
/ \ / \ / \ / \
i i i i i i i i
答案 0 :(得分：1)
waitpid()函数需要参数。
初始childpid = fork();是意料之外的。
你可以明智地写道：
for (int i = 0; i < 1; i++)
用于循环。
Start 46480
i am 46480, my parent is 30775
i am 46482, my parent is 46480
i am 46481, my parent is 46480
i am 46483, my parent is 46481
i am 46484, my parent is 46482
i am 46486, my parent is 46482
i am 46487, my parent is 46483
Exit 46487
i am 46488, my parent is 46484
Exit 46488
i am 46485, my parent is 46481
i am 46491, my parent is 46484
Exit 46491
i am 46489, my parent is 46483
Exit 46489
Exit 46483
i am 46492, my parent is 46486
Exit 46492
Exit 46484
i am 46490, my parent is 46486
Exit 46490
i am 46493, my parent is 46485
Exit 46493
Exit 46486
Exit 46482
i am 46494, my parent is 46485
Exit 46494
Exit 46485
Exit 46481
Exit 46480
#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/wait.h>
static pid_t fork_ok(void)
{
pid_t pid;
if ((pid = fork()) < 0)
{
fprintf(stderr, "Fork failure in pid %d\n", (int)getpid());
exit(1);
}
return pid;
}
int main(void)
{
fprintf(stderr, "Start %d\n", (int)getpid());
for (int level = 0; level < 3; level++)
{
if (fork_ok() == 0 || fork_ok() == 0)
continue;
break;
}
fprintf(stderr, "i am %d, my parent is %d\n",
(int)getpid(), (int)getppid());
while (wait(0) > 0)
;
fprintf(stderr, "Exit %d\n", (int)getpid());
return(0);
}
这使用了一个循环，一个有点不寻常的循环。在每个级别，父进程分叉两个孩子;孩子们每个'继续'到下一个级别，而父母完成并退出循环。清理代码与之前相同（见下文）。
#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/wait.h>
static pid_t fork_ok(void)
{
pid_t pid;
if ((pid = fork()) < 0)
{
fprintf(stderr, "Fork failure in pid %d\n", (int)getpid());
exit(1);
}
return pid;
}
static void new_level(int level)
{
if (level > 3)
return;
if (fork_ok() == 0 || fork_ok() == 0)
new_level(level+1);
else
{
printf("i am %d, my parent is %d\n",
(int)getpid(), (int)getppid());
while (wait(0) > 0)
;
printf("Exit %d\n", (int)getpid());
}
}
int main(void)
{
printf("Start %d\n", (int)getpid());
fflush(0);
new_level(0);
return(0);
}
我不相信你需要任何循环。这似乎对我有用：
Start 44397
i am 44397, my parent is 30775
i am 44400, my parent is 44397
i am 44401, my parent is 44397
Exit 44401
i am 44399, my parent is 44397
i am 44398, my parent is 44397
i am 44404, my parent is 44400
Exit 44404
i am 44403, my parent is 44399
i am 44402, my parent is 44398
i am 44405, my parent is 44398
i am 44407, my parent is 44398
Exit 44407
Exit 44400
i am 44406, my parent is 44399
Exit 44406
i am 44408, my parent is 44402
i am 44410, my parent is 44402
i am 44411, my parent is 44405
Exit 44410
Exit 44411
i am 44409, my parent is 44403
Exit 44409
Exit 44405
i am 44412, my parent is 44408
Exit 44412
Exit 44403
Exit 44399
Exit 44408
Exit 44402
Exit 44398
Exit 44397
#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/wait.h>
int main(void)
{
fprintf(stderr, "Start %d\n", (int)getpid());
if (fork() < 0 || fork() < 0 || fork() < 0 || fork() < 0)
{
fprintf(stderr, "Fork failure in pid %d\n", (int)getpid());
exit(1);
}
fprintf(stderr, "i am %d, my parent is %d\n",
(int)getpid(), (int)getppid());
while (wait(0) > 0)
;
fprintf(stderr, "Exit %d\n", (int)getpid());
return(0);
}