使用strcmp比较：

#include <stdio.h>
#include <string.h>int Compare(const char * file1, const char* file2)
{FILE* f1, * f2;int size1, size2;unsigned char buffer1[1024], buffer2[1024];f1 = fopen(file1, "rb+");f2 = fopen(file2, "rb+");size1 = fread(buffer1, 1, 1024, f1);size2 = fread(buffer2, 1, 1024, f2);printf("(%d)\n", size1);printf("(%d)\n", size1);printf("%s\n", buffer1);printf("%s\n", buffer2);if (strncmp(buffer1, buffer2, size1) == 0){return 1;}fclose(f1);fclose(f2);return 0;
}int main(int argc, char* argv[])
{if (Compare("1.txt", "2.txt")){printf("文件内容相同！\n");}else{printf("文件内容不相同！\n");}return 0;
}

通过字节比较：

#include<stdio.h>int Compare(const char * file1, const char* file2)
{FILE* f1, * f2;int size1, size2;unsigned char buffer1[1024], buffer2[1024];f1 = fopen(file1, "rb+");f2 = fopen(file2, "rb+");int isTheSame = 0;if (!f1)goto end;if (!f2)goto end;while (1){size1 = fread(buffer1, 1, 1024, f1);printf("(%s)\n", buffer1);size2 = fread(buffer2, 1, 1024, f2);if (size1 != size2){goto end;}if (size1 < 1)break;for (int i = 0; i < size1; i++){if (buffer1[i] != buffer2[i]){goto end;}}}isTheSame = 1;
end:if (f1)fclose(f1);if (f2)fclose(f2);return isTheSame;
}int main(int argc, char* argv[])
{if (Compare("1.txt", "2.txt")){printf("文件内容相同！\n");}else{printf("文件内容不相同！\n");}return 0;
}