用C语言实现1、输入线性表长度，并依次输入线性表的每一项。2、展示线性表中的内容。3、输入在第i个位置插入元素，输入元素值。4、展示线性表中的内容。5、输入在第i个位置删除元素，输入元素值。6、展示线性表中的内容

在C语言中，我们可以使用结构体表示线性表，并结合指针来实现上述功能。这里是一个简单的示例：

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

// 定义一个结构体表示线性表的节点
typedef struct Node {
    int data;
    struct Node* next;
} Node;

// 创建新节点并初始化
Node* createNode(int value) {
    Node* newNode = (Node*)malloc(sizeof(Node));
    if (newNode != NULL) {
        newNode->data = value;
        newNode->next = NULL;
    }
    return newNode;
}

// 插入节点到链表
void insertNode(Node** head, int position, int value) {
    if (position <= 0) {
        printf("Invalid position.\n");
        return;
    }

    Node* newNode = createNode(value);
    if (*head == NULL) {
        *head = newNode;
        return;
    }

    Node* current = *head;
    for (int i = 0; i < position - 1 && current != NULL; i++) {
        current = current->next;
    }
    if (current == NULL) {
        printf("Position out of range.\n");
        return;
    }
    newNode->next = current->next;
    current->next = newNode;
}

// 删除节点
void deleteNode(Node** head, int position, int valueToRemove) {
    if (*head == NULL || position <= 0) {
        printf("Invalid input.\n");
        return;
    }

    Node* prev = NULL;
    Node* current = *head;
    for (int i = 0; i < position - 1 && current != NULL; i++) {
        prev = current;
        current = current->next;
    }

    if (current == NULL || current->data != valueToRemove) {
        printf("Element not found or position invalid.\n");
        return;
    }

    if (prev == NULL) { // 如果删除的是头结点
        *head = current->next;
    } else {
        prev->next = current->next;
    }
}

// 显示链表内容
void displayList(Node* head) {
    if (head == NULL) {
        printf("The list is empty.\n");
    } else {
        Node* temp = head;
        while (temp != NULL) {
            printf("%d -> ", temp->data);
            temp = temp->next;
        }
        printf("NULL\n");
    }
}

int main() {
    Node* head = NULL;
    int length, position, value, index;

    printf("Enter the length of the linear list: ");
    scanf("%d", &length);

    // 输入并显示原始线性表内容
    for (int i = 0; i < length; i++) {
        printf("Enter element at position %d: ", i + 1);
        scanf("%d", &value);
        insertNode(&head, i + 1, value);
        displayList(head);
    }

    printf("Enter position to insert an element: ");
    scanf("%d", &position);
    printf("Enter value to insert: ");
    scanf("%d", &value);
    insertNode(&head, position, value);
    displayList(head);

    printf("Enter position to delete an element: ");
    scanf("%d", &position);
    printf("Enter value to delete: ");
    scanf("%d", &valueToRemove);
    deleteNode(&head, position, valueToRemove);
    displayList(head);

    return 0;
}

在这个示例中，我们首先创建一个链表，然后分别处理插入、删除和显示操作。注意这个程序假设用户提供的数据都是有效的，实际应用中需要添加错误检查和异常处理。