C语言：将归档文件每行存入数组后输出为0的问题求助

Let's walk through what's probably causing your output to show all zeros instead of the expected line content, and how to fix it:

Common Issues & Fixes #

1. You're Not Properly Processing the Comma-Separated Input #

Your input uses commas to split entries (1760 02/20/18,11403.7 02/19/18,...), so if you're trying to store each segment in a struct, you need explicit string-splitting logic. Skipping this step means your struct array stays unpopulated (or filled with garbage/zeros).

2. Unsafe String Copying (Missing Null Terminator) #

If you're using strcpy without length checks, or forgetting to add a null terminator, your struct's data array might end up with invalid data. strncpy is safer here, but it doesn't automatically add a null terminator—you have to do that manually to avoid weird output or crashes.

3. Wrong Printf Format Specifier #

Your output shows 1761 0 instead of the expected string—this is a clear sign you're using a numeric format specifier (like %d) instead of %s to print the data field. Printing a string with %d outputs the memory address as an integer, which often looks like zero.

4. Missing File Error Checking #

If your code doesn't verify the file opened successfully, you might be reading from a NULL file pointer. That means no data gets loaded into your array at all, leaving it filled with default zeros.

Corrected Code Example #

Here's a fixed version of your code that addresses all these problems:

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

typedef struct{
    char data[20];
} vetor;

int main(int argc, char *argv[]) {
    // Make sure a file path is provided as an argument
    if (argc < 2) {
        fprintf(stderr, "Usage: %s <archive_file_path>\n", argv[0]);
        exit(EXIT_FAILURE);
    }

    // Open the file with proper error handling
    FILE *fp = fopen(argv[1], "r");
    if (fp == NULL) {
        perror("Failed to open file");
        exit(EXIT_FAILURE);
    }

    vetor v[100]; // Adjust array size to match your needs
    int entry_count = 0;
    char line_buffer[1024];

    // Read the input line (assuming your archive has one line of comma-separated entries)
    if (fgets(line_buffer, sizeof(line_buffer), fp) != NULL) {
        // Split the line into individual entries using commas
        char *token = strtok(line_buffer, ",");
        while (token != NULL && entry_count < 100) {
            // Remove any trailing newline from the token
            token[strcspn(token, "\n")] = '\0';
            
            // Safely copy the token to the struct's data field
            strncpy(v[entry_count].data, token, sizeof(v[entry_count].data) - 1);
            // Manually add null terminator to avoid buffer overflow issues
            v[entry_count].data[sizeof(v[entry_count].data) - 1] = '\0';
            
            entry_count++;
            token = strtok(NULL, ",");
        }
    }

    fclose(fp);

    // Print the results with the correct format specifier
    for (int i = 0; i < entry_count; i++) {
        printf("%d %s\n", i + 1, v[i].data);
    }

    return 0;
}

Key Changes Explained #

• Added input validation to ensure a file path is provided, plus error checking for file opening
• Used strtok to split the comma-separated input into individual entries for the struct array
• Implemented safe string copying with strncpy and manual null termination to prevent buffer overflow
• Fixed the printf statement to use %s (the correct specifier for strings)
• Added logic to strip trailing newlines from each entry for clean output

内容的提问来源于stack exchange，提问作者Andre