如何用C语言实现文本文件中数据的对齐显示？

我写了一段C语言代码，用来将捐赠物资相关数据写入文本文件，但输出内容无法在对应列标题下对齐。以下是我的代码、当前输出，请求帮助实现数据列对齐。

原代码 #

#define _CRT_SECURE_NO_WARNINGS
#include <stdio.h>
#include <stdlib.h>
int main()
 {
    char name[5][30] = {"Contactless Thermometer","Hand Sanitizers",
                        "Face Mask", "Surgical Mask",
                            "Oxygen Mask"};
    char code[5][3] = {"CT","HS","FM","SM","OM"};
    char donator[5][15] = {"Japan","USA","China","China","Saudi Arabia"};
    int noOfShip[5] = {1,1,2,2,2};
    float qty[5] = {1.2,3.5,120,38,9};
    
    
    FILE *fptr;
    fptr = fopen("donations.txt","w");
    if(fptr == NULL)
    {
        printf("Error!");
        exit(1);
    }
   
    fprintf(fptr,"Name of Supply \t\t");
    fprintf(fptr,"Supply Code \t");
    fprintf(fptr,"Donator \t");
    fprintf(fptr,"No. of Shipment \t");
    fprintf(fptr,"Quantity Received (millions) \n");
    
    for(int i=0;i<5;i++)
    {
        fprintf(fptr,"%s \t",name[i]);
        fprintf(fptr,"%s \t",code[i]);
        fprintf(fptr,"%s \t",donator[i]);
        fprintf(fptr,"%d \t",noOfShip[i]);
        fprintf(fptr,"%.1f \n",qty[i]);
    }
    fclose(fptr);
    printf("file has been created successfully");
    return 0; 
}

当前输出 #

Name of Supply          Supply Code    Donator        No. of Shipment        Quantity Received (millions)
Contactless Thermometer         CT     Japan   1      1.2
Hand Sanitizers         HS      USA    1       3.5
Face Mask       FM      China   2      120.0
Surgical Mask   SM      China   2      38.0
Oxygen Mask     OM      Saudi Arabia   2       9.0

解决方案 #

问题根源在于用\t制表符分隔列，制表符宽度固定（通常为8字符），但不同内容长度差异会导致对齐错位。正确做法是使用格式化输出的宽度控制语法，给每列指定固定宽度，强制内容左对齐填充到对应宽度，就能实现完美对齐。

修改后的代码如下：

#define _CRT_SECURE_NO_WARNINGS
#include <stdio.h>
#include <stdlib.h>
int main()
 {
    char name[5][30] = {"Contactless Thermometer","Hand Sanitizers",
                        "Face Mask", "Surgical Mask",
                            "Oxygen Mask"};
    char code[5][3] = {"CT","HS","FM","SM","OM"};
    char donator[5][15] = {"Japan","USA","China","China","Saudi Arabia"};
    int noOfShip[5] = {1,1,2,2,2};
    float qty[5] = {1.2,3.5,120,38,9};
    
    
    FILE *fptr;
    fptr = fopen("donations.txt","w");
    if(fptr == NULL)
    {
        printf("Error!");
        exit(1);
    }
   
    // 用宽度控制输出标题，与数据列对应
    fprintf(fptr,"%-25s %-12s %-15s %-18s %-30s\n", 
            "Name of Supply", "Supply Code", "Donator", 
            "No. of Shipment", "Quantity Received (millions)");
    
    for(int i=0;i<5;i++)
    {
        // 对应每列宽度，-号表示左对齐
        fprintf(fptr,"%-25s %-12s %-15s %-18d %-30.1f\n", 
                name[i], code[i], donator[i], noOfShip[i], qty[i]);
    }
    fclose(fptr);
    printf("file has been created successfully");
    return 0; 
}

修改后的输出效果 #

Name of Supply             Supply Code   Donator          No. of Shipment       Quantity Received (millions)
Contactless Thermometer    CT            Japan            1                     1.2                         
Hand Sanitizers            HS            USA              1                     3.5                         
Face Mask                  FM            China            2                     120.0                       
Surgical Mask              SM            China            2                     38.0                        
Oxygen Mask                OM            Saudi Arabia     2                     9.0                         

格式说明 #

• %-Ns：左对齐（-为左对齐标记，默认右对齐），占用N个字符宽度，字符串不足时用空格填充
• %-Nd：针对整数类型的左对齐宽度控制
• %-N.Mf：针对浮点数，N为总宽度，M为小数位数，左对齐填充

你可以根据实际需求调整每列的宽度数值，确保标题和数据列完全对应。

内容的提问来源于stack exchange，提问作者Its Me