sprintf 不添加带有转义字符的字符串

Question

I have this function which gets the given directory and filename and concat it by checking if the end of the directory contains / character and concatenating the string's for condition. My problem is that when i give the function a directory name and filename if the filname has \ it does not concat the string correctly. but when if the file does not contain any \ the output will be given.How can i fix the issue?.

Here is my C Code.

char * find_endwith_slash(char *dir_path, char *file_name)
{
    char full_path[1024];
    if (dir_path[strlen(dir_path) - 1] != '/')
    {
        sprintf(full_path, "%s/%s", dir_path, file_name);
    }
    else
    {
        sprintf(full_path, "%s%s", dir_path, file_name);
    }

    char * full_name = malloc(strlen(full_path) * sizeof(char));
    full_name = strdup(full_path);

    return full_name;



} 

Answer 1

A more proper approach to conditionally concatenating path and file name:

char * find_endwith_slash_alt(const char *dir_path, const char *file_name) {
  size_t d_length = strlen(dir_path);
  size_t f_length = strlen(file_name);
  if (d_length > 0 && dir_path[d_length-1] == `/`) {
    d_length--;
  } 
  char *both = malloc(d_length + 1 + f_length + 1);
  if (both) {
    memcpy(both, dir_path, d_length);
    dir_path[d_length] = '/';
    memcpy(both + d_length + 1, file_name, f_length + 1);
  }
  return both;
}