如何创建unix进程二叉树? [英] How to create unix process binary trees?
问题描述
有人可以在这里帮助我，不一定完成我的作业.
Can some one help me out here, not necessarily complete my homework.
我需要使用fork()创建一个进程树；到目前为止，在Unix/C中，我能达到的最高水平是我的代码:
I need to create a process tree using fork(); in Unix/C so far the best I can get to to the 4th level here is my code:
/* 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，总体而言，编程很好，所以我想问一下公众我缺少哪些步骤.树的深度需要由用户指定，因此我认为我将使用一个for循环，但这只会在一个级别上相乘而不是创建新级别.
I am very new to C programming, well programming in general, so I wanted to ask the general public what steps I am missing. The tree depth needs to be user specified so I figured I would use n a for loop but that only multiplies across a level rather than creating new levels.
有人可以帮我指出正确的方向吗:) 我需要它像这样
Can someone help me out and point me in the right direction :) I need it to fork like this
i
/ \
/ \
/ \
/ \
/ \
i i
/ \ / \
/ \ / \
i i i i
/ \ / \ / \ / \
i i i i i i i i
推荐答案
waitpid() 函数需要参数.
The waitpid() function requires arguments.
最初的childpid = fork();是意外的.
您可以明智地写:
for (int i = 0; i < 1; i++)
循环，除非您坚持使用C89而不是C99语法.
for the loops unless you insist on using C89 instead of C99 syntax.
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
示例来源
#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);
}
这使用一个循环，这有点不寻常.在每个级别，父进程派生两个孩子；子级每个继续"到下一个级别，而父级完成并退出循环.清理代码与以前相同(请参见下文).
This uses a loop, a somewhat unusual loop. At each level, the parent process forks two children; the children each 'continue' to the next level, while the parent is done and exits the loop. The clean up code is the same as before (see below).
#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);
}
尝试1
我不认为您需要任何循环.这似乎对我有用:
Attempt 1
I'm not convinced you need any loops. This seemed to do the trick for me:
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
源代码
#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);
}
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