完整的fgets()解决方案:

#include <stdio.h>
#include <string.h>

#define MAX_LEN 256

int main(void)
{
    FILE* fp;
    fp = fopen("file.txt", "r");
    if (fp == NULL) {
      perror("Failed: ");
      return 1;
    }

    char buffer[MAX_LEN];
    while (fgets(buffer, MAX_LEN, fp))
    {
        // Remove trailing newline
        buffer[strcspn(buffer, "\n")] = 0;
        printf("%s\n", buffer);
    }

    fclose(fp);
    return 0;
}

输出:

First line of file
Second line of file
Third (and also last) line of file

记住，如果你想从标准输入(而不是像这种情况下的文件)中读取，那么你所要做的就是将stdin作为fgets()方法的第三个参数传递，就像这样:

while(fgets(buffer, MAX_LEN, stdin))

附录

从fgets()输入中删除尾随换行符

如何在c中检测文件是否打开

你犯了一个错误，返回了一个指向自动变量的指针。 变量行被分配到堆栈中，并且只在函数存在的时间内存在。 你不允许返回指向它的指针，因为一旦它返回，内存就会被分配到其他地方。

const char* func x(){
    char line[100];
    return (const char*) line; //illegal
}

为了避免这种情况，你可以返回一个指向堆上内存的指针。lineBuffer 当用户使用完free()时，调用它应该是用户的责任。 或者，您可以要求用户将写入行内容的内存地址作为参数传递给您。

我的工具从头开始:

FILE *pFile = fopen(your_file_path, "r");
int nbytes = 1024;
char *line = (char *) malloc(nbytes);
char *buf = (char *) malloc(nbytes);

size_t bytes_read;
int linesize = 0;
while (fgets(buf, nbytes, pFile) != NULL) {
    bytes_read = strlen(buf);
    // if line length larger than size of line buffer
    if (linesize + bytes_read > nbytes) {
        char *tmp = line;
        nbytes += nbytes / 2;
        line = (char *) malloc(nbytes);
        memcpy(line, tmp, linesize);
        free(tmp);
    }
    memcpy(line + linesize, buf, bytes_read);
    linesize += bytes_read;

    if (feof(pFile) || buf[bytes_read-1] == '\n') {
        handle_line(line);
        linesize = 0;
        memset(line, '\0', nbytes);
    }
}

free(buf);
free(line);

这个例子有一些错误:

you forgot to add \n to your printfs. Also error messages should go to stderr i.e. fprintf(stderr, .... (not a biggy but) consider using fgetc() rather than getc(). getc() is a macro, fgetc() is a proper function getc() returns an int so ch should be declared as an int. This is important since the comparison with EOF will be handled correctly. Some 8 bit character sets use 0xFF as a valid character (ISO-LATIN-1 would be an example) and EOF which is -1, will be 0xFF if assigned to a char. There is a potential buffer overflow at the line lineBuffer[count] = '\0'; If the line is exactly 128 characters long, count is 128 at the point that gets executed. As others have pointed out, line is a locally declared array. You can't return a pointer to it. strncpy(count + 1) will copy at most count + 1 characters but will terminate if it hits '\0' Because you set lineBuffer[count] to '\0' you know it will never get to count + 1. However, if it did, it would not put a terminating '\0' on, so you need to do it. You often see something like the following: char buffer [BUFFER_SIZE]; strncpy(buffer, sourceString, BUFFER_SIZE - 1); buffer[BUFFER_SIZE - 1] = '\0'; if you malloc() a line to return (in place of your local char array), your return type should be char* - drop the const.

这是我的几个小时…逐行读取整个文件。

char * readline(FILE *fp, char *buffer)
{
    int ch;
    int i = 0;
    size_t buff_len = 0;

    buffer = malloc(buff_len + 1);
    if (!buffer) return NULL;  // Out of memory

    while ((ch = fgetc(fp)) != '\n' && ch != EOF)
    {
        buff_len++;
        void *tmp = realloc(buffer, buff_len + 1);
        if (tmp == NULL)
        {
            free(buffer);
            return NULL; // Out of memory
        }
        buffer = tmp;

        buffer[i] = (char) ch;
        i++;
    }
    buffer[i] = '\0';

    // Detect end
    if (ch == EOF && (i == 0 || ferror(fp)))
    {
        free(buffer);
        return NULL;
    }
    return buffer;
}

void lineByline(FILE * file){
char *s;
while ((s = readline(file, 0)) != NULL)
{
    puts(s);
    free(s);
    printf("\n");
}
}

int main()
{
    char *fileName = "input-1.txt";
    FILE* file = fopen(fileName, "r");
    lineByline(file);
    return 0;
}

如果你的任务不是发明逐行读取函数，而只是逐行读取文件，你可以使用一个典型的代码片段，包括getline()函数(参见手册页):

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

int main(void)
{
    FILE * fp;
    char * line = NULL;
    size_t len = 0;
    ssize_t read;

    fp = fopen("/etc/motd", "r");
    if (fp == NULL)
        exit(EXIT_FAILURE);

    while ((read = getline(&line, &len, fp)) != -1) {
        printf("Retrieved line of length %zu:\n", read);
        printf("%s", line);
    }

    fclose(fp);
    if (line)
        free(line);
    exit(EXIT_SUCCESS);
}