Thread: Help with malloc and pointers.

Am I not doing that right now? That's what I'm attempting, at least...

Alright! I finally got the code mostly working.

Code:

#include <stdio.h>#include <sys/types.h>
#include <sys/stat.h>
#include <unistd.h>
#include <stdlib.h>
#include <string.h>


int filesize(char * filename)
{
    struct stat status;
    if (stat(filename, &status) == -1)
    {
        return -1;
    }
    else
    {
        return (int) status.st_size;
    }
}


int compare(const void *elem1, const void *elem2)
{
    char **e1 = (char **) elem1;
    char **e2 = (char **) elem2;
    if (strcmp(*e1,*e2)<0)
        return -1;
    else if (strcmp(*e1,*e2)>0)
        return 1;
    else
        return 0;
}


void sort(char **array, int size)
{
    qsort(&array[0], size, sizeof(array[0]), &compare);
}


int main(int argc, char * argv[])
{
    FILE *read;
    char in_name[255];
    int n = 0;
    int j = 0;
    int linecount = 1;

printf("What file should be read?\n");
    if (scanf("%s", in_name) != 1)
    {
printf("Invalid input.\n");
        return 1;
    }

    read = fopen(in_name,"r");

    if (read == NULL)
    {
printf("Cannot open input file.\n");
        return 1;
    }


    char * data = malloc(filesize(in_name));

    data[n] = fgetc(read);
    while (data[n] != EOF)
    {
        if (data[n] == '\n')
        {
            data[n] = '\0';
            linecount++;
        }
        data[++n] = fgetc(read);
    }
     if (data[n] != '\0')
         data[++n] = '\0';

    char ** lines = malloc(sizeof(lines[0]) * linecount);

    int i = 0;
    while (j < linecount)
    {
        lines[j] = &data[i];
        while(data[i] != '\0')
            i++;
        i++;
        j++;
    }


    sort(lines,linecount);

    for (int k = 0; k < linecount; k++)
    {
        printf("%s\n", lines[k]);
    }

    fclose(read);
    free(data);
    free(lines);
    return 0;
    }

The only problem is that the last line of my output gets \377 appended to it. It's definitely happening either when the data is being read or shortly after.

Ah, thank you so much! I've fixed it (as well as the over-complicated sort) and everything runs perfectly now.

For the final time, in case anyone needs it later, here's my code.

Code:

#include <stdio.h>#include <sys/types.h>
#include <sys/stat.h>
#include <unistd.h>
#include <stdlib.h>
#include <string.h>


int filesize(char * filename)
{
   struct stat status;
   if (stat(filename, &status) == -1)
   {
       return -1;
   }
   else
   {
       return (int) status.st_size;
   }
}




int compare(const void *elem1, const void *elem2)
{
   char **e1 = (char **) elem1;
   char **e2 = (char **) elem2;
   return strcmp(*e1,*e2);
}




void sort(char **array, int size)
{
   qsort(&array[0], size, sizeof(array[0]), &compare);
}




int main(int argc, char * argv[])
{
   FILE *read;
   char in_name[255];
   int n = 0;
   int j = 0;
   int linecount = 0;


printf("What file should be read?\n");
   if (scanf("%s", in_name) != 1)
   {
printf("Invalid input.\n");
       return 1;
   }


   read = fopen(in_name,"r");


   if (read == NULL)
   {
printf("Cannot open input file.\n");
       return 1;
   }




   char * data = malloc(filesize(in_name));


   data[n] = fgetc(read);
   while (data[n] != EOF)
   {
       if (data[n] == '\n')
       {
           data[n] = '\0';
           linecount++;
       }
       data[++n] = fgetc(read);
   }
    if (data[n] != '\0')
        data[++n] = '\0';


   char ** lines = malloc(sizeof(lines[0]) * linecount);
   int i = 0;
   while (j < linecount)
   {
       lines[j] = &data[i];
       while(data[i] != '\0')
           i++;
       i++;
       j++;
   }




   sort(lines,linecount);


   for (int k = 0; k < linecount; k++)
   {
       printf("%s\n", lines[k]);
   }


   fclose(read);
   free(data);
   free(lines);
   return 0;

   }