Linux的系统调用使用fork（）的传球整数到子和父进程的问题 [英] Linux System Calls problems using Fork() passing ints to child and parent processes
问题描述
我工作的一个程序，将采取一个整数，并创建两个过程，一个家长和一个孩子。家长会减去5从整数，它传递给谁将会由5划分它的孩子，那么他们将重复此过程5次，每次打印整数的当前值。
整数可以通过文本文件传递和被书面和读出的，或者管道可以使用这曾经是简单。
我一直在寻找了所需要的系统调用，并有一个半工作程序。我一直坚持了几个小时然而，我认为我的问题是，我不能让他们等待对方来完成，因为我的输出不正确。
下面是我得到那么远。
的#include＆LT;＆stdio.h中GT;
＃包括LT＆;＆unistd.h中GT;
＃包括LT＆;＆stdlib.h中GT;
＃包括LT＆; SYS / types.h中＆GT;
＃包括LT＆; SYS / wait.h＆GT;
＃包括LT＆;＆文件ctype.h GT;
＃包括LT＆;＆fcntl.h GT;INT主要（无效）
{
INT X = 19530;
INT W = 1;
INT FD [2];
管（FD）;
INT PID =叉（）; 时int k;
为（K = 0; K＆小于5; k ++）{
如果（PID大于0）{
// INT X = 19530; 如果（（接近（FD [0]））== - 1）{
PERROR（关闭）;
} 读（FD [0]，＆放大器; X，的sizeof（int）的）;
X = X-5;
写（FD [1]，＆放大器; X，的sizeof（int）的）;
的printf（X父％d个\\ N，X）; 关闭（FD [1]）;
关闭（FD [0]）;
}如果别人（PID == 0）{ 如果（（接近（FD [1]））== - 1）{
PERROR（关闭）;
} 读（FD [0]，＆放大器; X，的sizeof（int）的）;
X = X / 5;
的printf（X儿童％d个\\ N，X）;
写（FD [1]，＆放大器; X，的sizeof（int）的）; 关闭（FD [1]）;
关闭（FD [0]）;
}
}
返回0;
}
不过我的输出是一个问题，我得到：
X在父母19525
中X的孩子3905
关闭::错误的文件描述符
中X父19520
关闭::错误的文件描述符
中X父19515
关闭::错误的文件描述符
中X父19510
关闭::错误的文件描述符
中X父19505
关闭::错误的文件描述符
中X子781
关闭::错误的文件描述符
中X子156
关闭::错误的文件描述符
中X 31儿童
关闭::错误的文件描述符
中X子6
这似乎开始很好，但孩子赶上前，孩子不连续传回正确则父运行次数太多。我也一直试图解决坏的文件描述符，但无济于事。
任何帮助将大大AP preciated。
感谢。
的#include＆LT;＆stdio.h中GT;
＃包括LT＆;＆unistd.h中GT;
＃包括LT＆;＆err.h GT;＃定义OK（X）（{INT I_ =（X）;如果（I_ == -1）错误（1，＃X）; I_;}）枚举{P_，C_}; //父母，子女
枚举{R_，W_}; //读，写INT主要（无效）
{
INT X = 19530;
INT FD [2] [2];
INT PID; OK（管（FD [0]））;
确定（管道（FD [1]））; 确定（PID =叉（））; 关闭（FD [P _] [PID R_：W_？]）;
关闭（FD [C _] [PID W_：R_？]）; 的for（int i = 0;我小于5;我++）{
如果（PID）{
点¯x - = 5;
的printf（X父％d个\\ N，X）;
确定（写（FD [P _] [W_]，＆放大器; X，的sizeof（X）））;
OK（读（FD [C _] [R_]，和放大器; X，的sizeof（X）））;
}
其他{
确定（读（FD [P _] [R_]，＆放大器; X，的sizeof（X）））;
X / = 5;
的printf（X儿童％d个\\ N，X）;
OK（写（FD [C _] [W_]，和放大器; X，的sizeof（X）））;
}
}
返回0;
}
管道是单向的，所以你需要两个。我使用了一些枚举，试图使事情更容易阅读。
I am working on a program that will take an integer and create two processes, a parent and a child. The parent will subtract 5 from the integer, pass it to the child who will divide it by 5, and then they will repeat this process 5 times, each time printing the current value of the integer.
The integer can be passed through a text file and be both written and read off of, or a pipeline can be used which ever is simpler.
I have been looking up the systems calls needed, and have a semi working program. I have been stuck for hours however, and I think my issue is that I can't get them to wait for each other to finish because my output is incorrect.
Here is what I got so far.
#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <ctype.h>
#include <fcntl.h>
int main(void)
{
int x=19530;
int w=1;
int fd[2];
pipe(fd);
int pid = fork();
int k;
for (k=0; k<5; k++) {
if (pid>0) {
//int x = 19530;
if ((close(fd[0]))==-1) {
perror("Close:");
}
read(fd[0], &x, sizeof(int));
x=x-5;
write (fd[1], &x, sizeof(int));
printf("X in parent %d\n", x);
close(fd[1]);
close(fd[0]);
} else if (pid==0) {
if ((close(fd[1]))==-1) {
perror("Close:");
}
read(fd[0], &x, sizeof(int));
x=x/5;
printf("X in child %d\n", x);
write (fd[1], &x, sizeof(int));
close(fd[1]);
close(fd[0]);
}
}
return 0;
}
However my output is an issue, I am getting:
X in parent 19525
X in child 3905
Close:: Bad file descriptor
X in parent 19520
Close:: Bad file descriptor
X in parent 19515
Close:: Bad file descriptor
X in parent 19510
Close:: Bad file descriptor
X in parent 19505
Close:: Bad file descriptor
X in child 781
Close:: Bad file descriptor
X in child 156
Close:: Bad file descriptor
X in child 31
Close:: Bad file descriptor
X in child 6
It seems to start off well, but then the child doesn't pass back properly then the parent runs too many times in a row before the child catches up. I also been trying to fix that bad file descriptor but to no avail.
Any help would be greatly appreciated.
Thanks.
#include <stdio.h>
#include <unistd.h>
#include <err.h>
#define ok(x) ({ int i_ = (x); if (i_ == -1) err(1, #x); i_; })
enum { p_, c_ }; // parent, child
enum { r_, w_ }; // read, write
int main(void)
{
int x = 19530;
int fd[2][2];
int pid;
ok(pipe(fd[0]));
ok(pipe(fd[1]));
ok(pid = fork());
close(fd[p_][pid ? r_ : w_]);
close(fd[c_][pid ? w_ : r_]);
for (int i = 0; i < 5; i++) {
if (pid) {
x -= 5;
printf("X in parent %d\n", x);
ok(write(fd[p_][w_], &x, sizeof(x)));
ok(read(fd[c_][r_], &x, sizeof(x)));
}
else {
ok(read(fd[p_][r_], &x, sizeof(x)));
x /= 5;
printf("X in child %d\n", x);
ok(write(fd[c_][w_], &x, sizeof(x)));
}
}
return 0;
}
Pipes are unidirectional, so you need two. I used some enums to try and make things easier to read.
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