C语言文件拷贝-四种方式

利用文件IO的方式，实现2个文件的拷贝

int copy_by_fileIO(const char *dest_file_name, const char *src_file_name) {//OK
    int fd1 = open(dest_file_name,O_WRONLY|O_CREAT|O_APPEND,0766);
    if(fd1 == -1) {
        perror("fd1:");
        return -1;
    }
    int fd2 = open(src_file_name,O_RDONLY|S_IROTH);
    if(fd2 == -1) {
        perror("fd2:");
        return -1;
    }
    char *buffer = (char *)malloc(2 * sizeof(char));
    int ans = 0;
    int k;
    do{
        memset(buffer,0,sizeof(buffer));
        k = read(fd2,buffer,1);
        if(k  0);
    close(fd1);
    close(fd2);
    return ans;
}

利用标准IO的字符IO，实现2个文件的字节拷贝

int copy_by_char(const char *dest_file_name, const char *src_file_name) {//OK
    FILE *fp1 = fopen(dest_file_name,"w");
    FILE *fp2 = fopen(src_file_name,"r");
    if(fp1 == NULL) {
        perror("fp1:");
        return -1;
    }
    if(fp2 == NULL) {
        perror("fp2:");
        return -1;
    }
    char buffer = fgetc(fp2);
    int cnt = 0;
    while(!feof(fp2)) {
        cnt++;
        fputc(buffer,fp1);
        buffer = fgetc(fp2);
    }
    fclose(fp1);
    fclose(fp2);
    return cnt;
}

利用标准IO的行IO，实现2个文件的按行拷贝

int copy_by_line(const char *dest_file_name, const char *src_file_name) { //ok
    FILE *fp1 = fopen(dest_file_name,"w");
    FILE *fp2 = fopen(src_file_name,"r");
    if(fp1 == NULL) {
        perror("fp1:");
        return -1;
    }
    if(fp2 == NULL) {
        perror("fp2:");
        return -1;
    }
    char * buffer = (char *)malloc(sizeof(char) * 101);
    int cnt = 0;
    while(fgets(buffer,100,fp2)) {
        fputs(buffer,fp1);
        cnt++;
    }
    free(buffer);
    fclose(fp1);
    fclose(fp2);
    return cnt;//返回的是读取的行数
}

利用标准IO的块IO，实现2个文件的块拷贝

int copy_by_block(const char *dest_file_name, const char *src_file_name) {//ok
    FILE *fp1 = fopen(dest_file_name,"w");
    FILE *fp2 = fopen(src_file_name,"r");
    if(fp1 == NULL) {
        perror("fp1:");
        return -1;
    }
    if(fp2 == NULL) {
        perror("fp2:");
        return -1;
    }
    void *buffer = (void *)malloc(2);
    int cnt = 0;
    while(1) {
        int op = fread(buffer,1,1,fp2);
        if(op