也算實驗出來了吧,不過還好有網絡,不然好多自己解決不了的問題真就解決不了了。我先寫了個這樣的建立多個子程序的程式(模仿書上建立一個程序的程式):
#include <stdio.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <stdlib.h>
int main(void)
{
pid_t childpid1, childpid2, childpid3;
int status;
int num;
childpid1 = fork();
childpid2 = fork();
childpid3 = fork();
if( (-1 == childpid1)||(-1 == childpid2)||(-1 == childpid3))
{
perror("fork()");
exit(EXIT_FAILURE);
}
else if(0 == childpid1)
{
printf("In child1 process\n");
printf("\tchild pid = %d\n", getpid());
exit(EXIT_SUCCESS);
}
else if(0 == childpid2)
{
printf("In child2 processd\n");
printf("\tchild pid = %d\n", getpid());
exit(EXIT_SUCCESS);
}
else if(0 == childpid3)
{
printf("In child3 process\n");
printf("\tchild pid = %d\n", getpid());
exit(EXIT_SUCCESS);
}
else
{
wait(NULL);
puts("in parent");
// printf("\tparent pid = %d\n", getpid());
// printf("\tparent ppid = %d\n", getppid());
// printf("\tchild process exited with status %d \n", status);
}
exit(EXIT_SUCCESS);
}
結果搞出兩個僵屍來,怎麼都想不明白,最後在網上找到了答案。并來回揣摩出來了方法和注意事項:
#include <stdio.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <stdlib.h>
int main(void)
{
pid_t childpid1, childpid2, childpid3;
int status;
int num;
/* 這裡不可以一下就建立完子程序,要用
*要 建立-》判斷-》使用-》return or exit.更不能這樣如test2.c
*childpid1 = fork();
*childpid2 = fork();
*childpid3 = fork();
*/
childpid1 = fork(); //建立
if(0 == childpid1) //判斷
{ //進入
printf("In child1 process\n");
printf("\tchild pid = %d\n", getpid());
exit(EXIT_SUCCESS); //退出
}
childpid2 = fork();
if(0 == childpid2)
{
printf("In child2 processd\n");
printf("\tchild pid = %d\n", getpid());
exit(EXIT_SUCCESS);
}
childpid3 = fork();
if(0 == childpid3)
{
printf("In child3 process\n");
printf("\tchild pid = %d\n", getpid());
exit(EXIT_SUCCESS);
}
//這裡不可以用wait(NULL),多個子程序是不可以用wait來等待的,它隻會等待一個 其它都成僵屍了
waitpid(childpid1, NULL, 0);
waitpid(childpid2, NULL, 0);
waitpid(childpid3, NULL, 0);
puts("in parent");
exit(EXIT_SUCCESS);
}
嚴格照着這樣做就不會出現 僵屍,也不會影響其它程序。
建立-》判斷-》使用-》return or exit.