c - 从文件中读取多行到 C 中的字符串

Question

如何从文本文件(可变宽度)中读取多行并将它们全部存储在 C“字符串”中？

编辑:我想我会 fget'ing 字符串并将它们存储在一个灵活的缓冲区中(通过 realloc):) 另外，这不是家庭作业，尽管它看起来确实如此(编程对我来说只是一种爱好) .我只是出于好奇才问的

Answer 1

因为这显然不是家庭作业，下面是一些示例代码，说明我将如何做。我只是为整个文件分配一个巨大的内存块，因为无论如何你最终都会读取整个文件，但如果你正在处理大文件，通常最好一次处理它们。

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

int main(int argc, char *argv[])
{
        // first, get the name of the file as an argument
        if (argc != 2) {
                printf("SYNTAX: %s <input file>\n", argv[0]);
                return -1;
        }

        // open the file
        FILE* fp = fopen(argv[1], "r");

        if (fp == NULL) {
                printf("ERROR: couldn't open file\n");
                return -2;
        }

        // seek to the end to get the length
        // you may want to do some error-checking here
        fseek(fp, 0, SEEK_END);
        long length = ftell(fp);

        // we need to seek back to the start so we can read from it
        fseek(fp, 0, SEEK_SET);

        // allocate a block of memory for this thing
        // the +1 is for the nul-terminator
        char* buffer = malloc((length + 1) * sizeof(char));

        if (buffer == NULL) {
                printf("ERROR: not enough memory to read file\n");
                return -3;
        }

        // now for the meat. read in the file chunk by chunk till we're done
        long offset = 0;
        while (!feof(fp) && offset < length) {
                printf("reading from offset %d...\n", offset);
                offset += fread(buffer + offset, sizeof(char), length-offset, fp);
        }

        // buffer now contains your file
        // but if we're going to print it, we should nul-terminate it
        buffer[offset] = '\0';
        printf("%s", buffer);

        // always close your file pointer
        fclose(fp);

        return 0;
}

哇，自从我编写 C 代码以来已经有一段时间了。希望人们会提出有用的更正/大量问题的通知。 :)