如何拼接字符指针？C语言调用system()执行xcopy时参数拼接失败问题解决

Ah, I get it—you're tripping over a key difference between C and Java when it comes to string handling. Let's break this down and fix your code.

Your original code fails because C doesn't support string concatenation with the + operator like Java does. In Java, String objects have the + operator overloaded to combine strings seamlessly, but in C, when you write "xcopy "+source+destination, you're actually doing pointer arithmetic—not string joining. That expression calculates an invalid memory address, which is why system() can't execute the command properly.

Solution 1: Use snprintf (Recommended for Safety) #

The safest way to build your command string is to use snprintf, which lets you write formatted text into a buffer while respecting its size to avoid overflow. Here's how to do it:

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

int main() {
    char *source = "D:\\SOFTWARE\\Internet";
    char *destination = " D:\\test /s /e /d /y";
    
    // Calculate the total length needed for the command string
    size_t total_length = strlen("xcopy ") + strlen(source) + strlen(destination) + 1;
    // +1 accounts for the null terminator that ends every C string
    
    // Allocate memory dynamically for the command
    char *command = (char*)malloc(total_length);
    if (command == NULL) {
        perror("Failed to allocate memory");
        return 1;
    }
    
    // Build the full xcopy command
    snprintf(command, total_length, "xcopy %s%s", source, destination);
    
    // Execute the command
    system(command);
    
    // Don't forget to free the allocated memory!
    free(command);
    return 0;
}

Solution 2: Use a Fixed-Size Buffer (Simpler for Short Paths) #

If you're confident your source and destination paths won't be excessively long, you can use a fixed-size character array instead of dynamic memory:

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

int main() {
    char *source = "D:\\SOFTWARE\\Internet";
    char *destination = " D:\\test /s /e /d /y";
    
    // Choose a buffer size large enough to hold your command (adjust as needed)
    char command[512];
    
    // Build the command into the buffer
    snprintf(command, sizeof(command), "xcopy %s%s", source, destination);
    
    // Run the command
    system(command);
    return 0;
}

Key Notes: #

• Always prefer snprintf over sprintf—snprintf prevents buffer overflow by limiting the number of characters written, which avoids crashes or potential security issues.
• In C, strings are just arrays of characters terminated by a null byte (\0). You can't "add" pointers together to combine strings; you have to manually copy or format them into a single buffer.

内容的提问来源于stack exchange，提问作者coder_hasib