写一个简单的linux文本io加密/解密代码

以下是一个简单的Linux文本IO加密/解密代码的示例，使用了XOR算法：

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

#define BUFFER_SIZE 1024

void xor_encrypt(char *data, int data_len, const char *key, int key_len) {
    int i;
    for(i = 0; i < data_len; i++) {
        data[i] = data[i] ^ key[i % key_len];
    }
}

void xor_decrypt(char *data, int data_len, const char *key, int key_len) {
    int i;
    for(i = 0; i < data_len; i++) {
        data[i] = data[i] ^ key[i % key_len];
    }
}

void encrypt_file(const char *in_filename, const char *out_filename, const char *key) {
    char buffer[BUFFER_SIZE];
    int bytes_read, bytes_written;
    FILE *in_file = fopen(in_filename, "r");
    FILE *out_file = fopen(out_filename, "w");

    // Encrypt file
    while ((bytes_read = fread(buffer, 1, BUFFER_SIZE, in_file)) > 0) {
        xor_encrypt(buffer, bytes_read, key, strlen(key));
        bytes_written = fwrite(buffer, 1, bytes_read, out_file);
    }

    fclose(in_file);
    fclose(out_file);
}

void decrypt_file(const char *in_filename, const char *out_filename, const char *key) {
    char buffer[BUFFER_SIZE];
    int bytes_read, bytes_written;
    FILE *in_file = fopen(in_filename, "r");
    FILE *out_file = fopen(out_filename, "w");

    // Decrypt file
    while ((bytes_read = fread(buffer, 1, BUFFER_SIZE, in_file)) > 0) {
        xor_decrypt(buffer, bytes_read, key, strlen(key));
        bytes_written = fwrite(buffer, 1, bytes_read, out_file);
    }

    fclose(in_file);
    fclose(out_file);
}

int main(int argc, char *argv[]) {
    if (argc != 4) {
        printf("Usage: %s <input file> <output file> <key>\n", argv[0]);
        exit(EXIT_FAILURE);
    }

    const char *in_filename = argv[1];
    const char *out_filename = argv[2];
    const char *key = argv[3];

    encrypt_file(in_filename, "encrypted.tmp", key);
    decrypt_file("encrypted.tmp", out_filename, key);
    remove("encrypted.tmp");

    printf("File %s encrypted and decrypted successfully.\n", in_filename);
    return 0;
}

这个例子中，我们使用了XOR算法来加密和解密文件。我们实现了两个函数`xor_encrypt`和`xor_decrypt`用于加密和解密数据，另外我们实现了`encrypt_file`和`decrypt_file`函数来加密和解密文件。我们还实现了一个简单的命令行接口，可以通过传递输入文件、输出文件和密钥来使用这些函数加密和解密文件。