I've been tasked with remaking a portion of the functionality of the find command. The first part I'm trying to do is just the normal "find " where it lists all files and sub-directories within that directory. I'm using the actual find command to test my results.

Anything apparent that I'm missing that's causing me to print improper file paths?

Image Order:

1. C Code

2. Expected Output

3. Actual Output

4. Tree for the directory I'm using to test

   void readSub (char* subDir)
   {
    DIR *sub_dp = opendir(subDir); //Opens directory stream
   
    struct dirent *subDirp; //define sub directory pointer
    struct stat buf; //define file status struct
   
    char t1[] = ".";
    char t2[] = "..";
    char t3[] = "/";
   
    if(sub_dp != NULL) // Was directory successfully opened
    {
            //read each entry one time only
            while((subDirp = readdir(sub_dp)) != NULL)
            {
                    char *temp = subDirp -> d_name; //check if first entry was a sub directory
   
                    //avoid searching for . and ..
                    if(strcmp(temp, t1) != 0 && strcmp(temp, t2) != 0)
                    {
                            char *tempSub = t3;
                            tempSub = strcat(tempSub, temp); //add / to entry name
                            char *temp_full_path = malloc(sizeof(char) * 2000);
                            temp_full_path = strcpy(temp_full_path, subDir);
                            strcat(temp_full_path, tempSub); //gives full path
   
                            printf("%s\n", temp_full_path);
                            DIR *subsubDP = opendir(temp_full_path); //try to open
   
                            if(subsubDP != NULL) //if not NULL then subsubDP is sub directory
                            {
                                    closedir(subsubDP); //will get opened in recursive call
                                    readSub(temp_full_path); //recursive call
                            }
                    }
            } //end of while loop
            closedir(sub_dp); //close directory stream
    }
   
    else
    {
            printf("Can't open directory\n");
            exit(2);
    }
   }
   
   int main(int argc, char **argv)
   {
           char *dir;
   
    if(argc < 2)
    {
            dir = ".";
    }
   
    else
    {
            dir = argv[1];
    }
   
    readSub(dir);
   
    exit(0);
   }
   

CodePudding user response：

The problem is

tempSub = strcat(tempSub, temp); //add / to entry name

tempSub points to the t3 array, which only has 2 bytes. Concatenating temp to it writes outside the array bounds, which causes undefined behavior.

You should calculate the total length of temp_full_path by adding the lengths of subDir, t3, temp, plus 1 for the null terminator, and allocate that. Since you only need this within the current loop iteration, you can use a variable-length array rather than malloc() (your code never calls free(temp_full_path)).

Replace

 char *tempSub = t3;
 tempSub = strcat(tempSub, temp); //add / to entry name
 char *temp_full_path = malloc(sizeof(char) * 2000);
 temp_full_path = strcpy(temp_full_path, subDir);
 strcat(temp_full_path, tempSub); //gives full path

with

char temp_full_path[strlen(subDir)   strlen(t3)   strlen(temp)   1];
sprintf(temp_full_path, "%s%s%s", subDir, t3, temp);