用C语言写出一段程序：将两个升序链表合并为一个新的 升序 链表并返回。新链表是通过拼接给定的两个链表的所有节点组成的。

好的，以下是用C语言实现两个链表合并的代码：

#include <stdio.h>
#include <stdlib.h>

struct ListNode {
    int val;
    struct ListNode *next;
};

struct ListNode* mergeTwoLists(struct ListNode* l1, struct ListNode* l2){
    struct ListNode *dummy = (struct ListNode *)malloc(sizeof(struct ListNode));
    struct ListNode *tail = dummy;

    while (l1 != NULL && l2 != NULL) {
        if (l1->val <= l2->val) {
            tail->next = l1;
            l1 = l1->next;
        }
        else {
            tail->next = l2;
            l2 = l2->next;
        }
        tail = tail->next;
    }
    tail->next = l1 != NULL ? l1 : l2;

    struct ListNode *head = dummy->next;
    free(dummy);

    return head;
}

int main() {
    // example usage
    // create two sorted linked lists
    struct ListNode *l1 = (struct ListNode *)malloc(sizeof(struct ListNode));
    struct ListNode *l2 = (struct ListNode *)malloc(sizeof(struct ListNode));
    l1->val = 1;
    l1->next = (struct ListNode *)malloc(sizeof(struct ListNode));
    l1->next->val = 2;
    l1->next->next = (struct ListNode *)malloc(sizeof(struct ListNode));
    l1->next->next->val = 4;
    l1->next->next->next = NULL;

    l2->val = 1;
    l2->next = (struct ListNode *)malloc(sizeof(struct ListNode));
    l2->next->val = 3;
    l2->next->next = (struct ListNode *)malloc(sizeof(struct ListNode));
    l2->next->next->val = 4;
    l2->next->next->next = NULL;

    // merge the two linked lists
    struct ListNode *merged = mergeTwoLists(l1, l2);

    // print the merged linked list
    while (merged != NULL) {
        printf("%d ", merged->val);
        merged = merged->next;
    }
    printf("\n");

    return 0;
}

这个程序创建了两条升序链表，然后调用 `mergeTwoLists` 函数将它们合并为一条新的升序链表并将其打印出来。

注意，这个程序使用了链表数据结构和动态内存分配。如果你对这些概念不熟悉，可能需要先学习一些相关的基础知识。