用c实现getline

以下是用C语言实现getline函数的示例代码：

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

char *getline(void) {
    char *line = NULL;
    char ch;
    int len = 0;
    int size = 1;

    // allocate memory for the line
    line = (char *) malloc(size * sizeof(char));
    if (line == NULL) {
        printf("Error: unable to allocate memory for the line\n");
        exit(1);
    }

    // read characters from stdin until new line or end of file
    while ((ch = getchar()) != '\n' && ch != EOF) {
        // resize the line if necessary
        if (len >= size) {
            size *= 2;
            line = (char *) realloc(line, size * sizeof(char));
            if (line == NULL) {
                printf("Error: unable to resize memory for the line\n");
                exit(1);
            }
        }
        // add the character to the line
        line[len++] = ch;
    }

    // add null terminator to the line
    line[len] = '\0';

    return line;
}

int main() {
    char *line;

    printf("Enter a line of text: ");
    line = getline();
    printf("The line you entered is: %s\n", line);

    free(line);
    return 0;
}

这个getline函数实现了从标准输入读取一行字符串，并将其存储在动态分配的内存中。如果在读取过程中需要重新分配内存，则使用realloc函数来增加内存大小。函数返回一个指向动态分配的内存的指针，需要在使用完后调用free函数来释放内存。