C语言结构体存储姓名后格式化打印无输出问题排查

我编写了一个程序，从标准输入读取按换行分隔的名（firstName）和姓（lastName），存入结构体数组的字符数组中。读取存储环节看似正常，但按<lastName>, <firstName>格式打印时出现异常：使用printf("%s, %s",people[0].lastName, people[0].firstName);无任何输出；但将两个字符串分开换行打印，或用puts打印时却能正常输出。注释掉removeNewline()函数后，格式化打印恢复正常，但字符串末尾会带有换行符，无法达到预期输出格式。

完整代码如下：

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

#define MAX_STRING_LENGTH 100
#define MAX_PEOPLE 42

struct Person{
  char firstName [MAX_STRING_LENGTH];
  char lastName[MAX_STRING_LENGTH];
};

void removeNewline(char * string){
  for(int i = 0; string[i] != '\0'; i++){
    if(string[i] == '\n'){
      string[i] = '\0';
    }
  }
}

int parseData(struct Person * people){
    int peopleCounter;
    for(peopleCounter = 0; peopleCounter < MAX_PEOPLE; peopleCounter++){
        char firstName[MAX_STRING_LENGTH];
        char lastName[MAX_STRING_LENGTH];

      if(fgets(firstName,MAX_STRING_LENGTH,stdin) == NULL){
        break;
      }
      fgets(lastName,MAX_STRING_LENGTH,stdin);
        
      removeNewline(firstName);
      removeNewline(lastName);

      strcpy(people[peopleCounter].firstName,firstName);
      strcpy(people[peopleCounter].lastName,lastName);
    }
    return peopleCounter;
}

int main(int argc, char *argv[]){

    struct Person people [MAX_PEOPLE];
    parseData(people);

    //PROBLEM
    printf("%s, %s",people[0].firstName, people[0].lastName);

    for(int i = 0; i < 2; i++){
        printperson(people, i);
    }
}

运行命令：./main <people.txt，people.txt示例内容：

George
Washington
Thomas
Jefferson

预期输出：

Washington, George
Jefferson, Thomas

1. 核心问题：removeNewline未处理Windows风格换行符 #

如果你的文本文件是Windows格式，每行末尾是\r\n（回车+换行），原函数只将\n替换为\0，但\r会留在字符串末尾。当printf输出时，\r会让光标跳回行首，后续的, %s会覆盖之前的输出，导致看起来没有内容。

同时原函数用循环遍历的方式效率低，改用strchr定位换行符更简洁可靠。修改后的removeNewline函数：

void removeNewline(char * string){
    char *newline = strchr(string, '\n');
    if (newline != NULL) {
        // 处理Windows风格的\r\n换行
        if (newline > string && *(newline - 1) == '\r') {
            *(newline - 1) = '\0';
        } else {
            *newline = '\0';
        }
    }
}

2. 打印参数顺序错误 #

预期输出是姓, 名，但原代码中printf的参数顺序写反了，改成：

printf("%s, %s\n", people[0].lastName, people[0].firstName);

加上\n保证输出换行，符合预期格式。

3. 补全缺失的printperson函数 #

原代码调用了未定义的printperson函数，会导致编译错误，补全该函数：

void printperson(struct Person *people, int index) {
    printf("%s, %s\n", people[index].lastName, people[index].firstName);
}

4. 完善输入读取的异常处理 #

读取lastName时也需检查fgets的返回值，避免文件行数为奇数时出错：

if(fgets(firstName,MAX_STRING_LENGTH,stdin) == NULL){
    break;
}
if(fgets(lastName,MAX_STRING_LENGTH,stdin) == NULL){
    break;
}

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

#define MAX_STRING_LENGTH 100
#define MAX_PEOPLE 42

struct Person{
    char firstName[MAX_STRING_LENGTH];
    char lastName[MAX_STRING_LENGTH];
};

void removeNewline(char *string){
    char *newline = strchr(string, '\n');
    if (newline != NULL) {
        if (newline > string && *(newline - 1) == '\r') {
            *(newline - 1) = '\0';
        } else {
            *newline = '\0';
        }
    }
}

void printperson(struct Person *people, int index) {
    printf("%s, %s\n", people[index].lastName, people[index].firstName);
}

int parseData(struct Person *people){
    int peopleCounter;
    for(peopleCounter = 0; peopleCounter < MAX_PEOPLE; peopleCounter++){
        char firstName[MAX_STRING_LENGTH];
        char lastName[MAX_STRING_LENGTH];

        if(fgets(firstName, MAX_STRING_LENGTH, stdin) == NULL){
            break;
        }
        if(fgets(lastName, MAX_STRING_LENGTH, stdin) == NULL){
            break;
        }
        
        removeNewline(firstName);
        removeNewline(lastName);

        strcpy(people[peopleCounter].firstName, firstName);
        strcpy(people[peopleCounter].lastName, lastName);
    }
    return peopleCounter;
}

int main(int argc, char *argv[]){
    struct Person people[MAX_PEOPLE];
    int count = parseData(people);

    printf("%s, %s\n", people[0].lastName, people[0].firstName);

    for(int i = 0; i < count; i++){
        printperson(people, i);
    }
    return 0;
}

运行后即可得到预期输出：

Washington, George
Washington, George
Jefferson, Thomas

（注：main中的单独打印和循环打印会重复第一行，可根据需求移除其中一个）

内容的提问来源于stack exchange，提问作者startler03