我将尝试编写一个C++程序,创建一个子进程,运行一个命令并将输出管道返回到父进程正在运行的命令的输入。
我已经让父进程执行了wait(NULL)或wait((void*)pid)命令,但它并没有等待。
以下是代码:
我已经让父进程执行了wait(NULL)或wait((void*)pid)命令,但它并没有等待。
以下是代码:
#include <string.h>
#include <fstream>
#include <iostream>
#include <unistd.h>
#include <stdio.h>
#include <sys/wait.h>
using namespace std;
int main(int argc, char * argv[])
{
char* commands[strlen(argv[1])];
char *command = NULL;
command = strtok(argv[1],"|");
int i = 0;
while(command != NULL)
{
commands[i] = command;
i++;
command = strtok(NULL,"|");
}
int numberOfCommands = i;
pid_t pid;
int pfd[2];
char* prgname = NULL;
if(pipe(pfd) == -1)
{
perror("error on pipe call");
return(1);
}
for(int j = 0;j<numberOfCommands;j++)
{
cout<<commands[j]<<endl;
}
pid = fork();
if(pid == 0){//child process
printf("Child: My PID = %d\n", getpid());
printf("Child: Running...\n");
close(pfd[0]); //close read end of pipe
dup2(pfd[1],1);//connect the pipes
close(pfd[1]);//close extra file descriptors
prgname = commands[0];//first command
cout<<"child starting command: "<<prgname<<endl;
execlp(prgname, prgname, 0);//Load the program
**printf("Child: Done sleeping, returning.\n");**
}
else
{
printf("Parent: My PID = %d\n", getpid());
**wait((void*)pid); //also tried wait(NULL); same effect
printf("Parent: Running...\n");**
close(pfd[1]); //close the write end of the pipe
dup2(pfd[0],0);//connect the pipes
close(pfd[0]); //close extra file descriptor
prgname = commands[1];//now run the second command
cout<<"parent starting command: "<<prgname<<endl;
execlp(prgname, prgname, 0);//Load the programm
}
cout<<"all done"<<endl;
return 0;
}
请注意加粗的行。我期望父进程在wait()命令处等待,子进程会打印出“Child done sleeping...”,然后结束,然后父进程会打印出“Parent: running...”。
我做错了什么!
谢谢!
更新:程序的完整输出如下:
dmegs
more
Child: My PID = 30070
Child: Running...
Parent: My PID = 30066
Parent: Running...
parent starting command: more
child starting command: dmegs
Child: Done sleeping, returning.
all done