在C中将进程放在后台

Question

我目前潜入创建一个backgrounding工作C用&.我需要实现非阻塞waitpid才能使其正常工作.我知道.此外,如果&在命令行末尾输入,我已经抓住了这个条件.我只是不确定如何准确地将进程作为后台作业发送,并将其实现为执行,而另一个提示是提示下一个命令.
任何事情都会有所帮助,谢谢.

    struct bgprocess{
        int pid;
        struct bgprocess * next;
        struct bgprocess * prev;    
    };

    struct bgprocess * bgprocess1;
    bgprocess1 = malloc(sizeof(struct bgprocess));
    bgprocess1->prev = NULL;
    bgprocess1->next = NULL;
    bgprocess1->pid = NULL;

    struct bgprocess * current;
    current = bgprocess1;

    do{
        int bgreturn = 0;
        while (current != NULL){
            if (waitpid(current->pid, &bgreturn, WNOHANG)){
                printf("Child exited");
                current->prev->next = current->next;
                current->next->prev = current->prev;
                current->prev = NULL;
                current->next = NULL;
                free(current);                  
            }
        current = current->next;    
        }
        if (end){
            int pid = fork();
            if (pid < 0){
                exit(1);            
            }       
            if (pid) {
                execvp(args[0], args);          
                exit(0);            
            }

            struct bgprocess * newNode;
            newNode = malloc(sizeof(struct bgprocess));
            newNode->pid = pid;
            newNode->next = NULL;

            if (current->next == NULL){
                current->next = newNode;        
            }
            while (1){
                if (current->next == NULL){
                    current->next = newNode;
                }           
                current = current->next;
            }

        }
    }
    while (current != NULL);

    int bgreturn = 0;
    while (current != NULL){
        if (waitpid(current->pid, &bgreturn,0)){
            printf("Child exited");
            current->prev->next = current->next;
            current->next->prev = current->prev;
            current->prev = NULL;
            current->next = NULL;
            free(current);  
        }
        current = current->next;
    }
    }

好吧,所以我一直在研究这个问题,我想我可能已经开始明白了.我仍然有一些语法错误,我不知道如何修复所以我可能会使用gdb或其他东西,除非别人可以指出它们.我是以正确的方式去做还是我完全错了？

Answer 1

听起来你正在实现一个shell.

只需使用fork来创建一个子进程 - 它将是并发的.从那里,你可以使用的EXEC*系列执行任何你喜欢的可执行文件,或者干脆运行在孩子的C代码而父返回并提示更多的信息(下一个命令等)使用等待在顶部的WNOHANG选项循环检查已终止的孩子,并在最后为这些孩子的其余部分再次(这次没有WNOHANG).

我必须鼓励你不要让它变得比实际更复杂.用简单的英语(或你的母语,或伪代码)写出你想要的东西,然后用最少的聪明才能把它翻译成C.

(伪)代码:

struct child {
    int pid;
    struct child * next;
    struct child * prev;
}
struct child * children = null;
do {
    int return = 0;
    struct child * curr = children;
    while(curr != null){
        if(waitpid(curr->pid, &return, WNOHANG)){
            //Report child exited with return status 'return'
            //Remove child (linked list style)
         }
         curr = curr->next;
     }
     /* PROMPT, ETC */
     if ( doInBackground ){
         int pid = fork();
         if(pid <0 )exit(); //error
         if(pid){
             //Child
             execvp(processName, arrayOfArgs);
             //This should never get executed
             exit();
         }
         //Add pid (linked list style, again)
     }
}while(!exitCondition)

int return = 0;
struct child * curr = children;
while(curr != null){
    if(waitpid(curr->pid, &return, 0)){
        //Report child exited with return status 'return'
        //Remove child (linked list style)
    }
    curr = curr->next;
}