#include <string.h>
#include <stdlib.h>
#include <stdio.h>


/*  uni() function takes an array an thier size.and it produce an array which is include unique element  */
int uni(char **arr,int size)
{
  int unique = 0; /* The length of dst after removing duplicates */
  int n=size;
  char *dst[n];     /* The set of stirings without duplicates */
  int i;

  /* The first number is never a duplicate */
  dst[unique++] = arr[0];

  /* Load the unique strings into the destination list */
  for ( i = unique; i < n; i++ ) {
    int has_dup = 0;
    int j;

    for ( j = 0; j < unique; j++ ) {
      if ( arr[i] == dst[j] )
        has_dup = 1;
    }

    if ( has_dup == 0 )
      dst[unique++] = arr[i];
  }

 /* Display the unique strings*/
   for ( i = 0; i < unique; i++ )
    printf ( "%s ", dst[i] );
  printf ( "\n" );

  return 0;
}

int main ( void )
{
   static const char filename[] = "input1.txt";    
   char colour[20],name[20];
   char *image[1000];

   int i=0,h,x,y,w;
   FILE *file = fopen ( filename, "r" );
   if ( file != NULL )
   {
      char line [ 128 ]; /* or other suitable maximum line size */

      while ( fgets ( line, sizeof line, file ) != NULL ) /* read a line */
      {         
	sscanf(line,"%s%d%d%d%d%s",name,&w,&h,&x,&y,colour); 

               image[i]=colour;
               i++;
      }
      uni(image,1000);
	
      fclose ( file );
   }
   else
   {
      perror ( filename ); /* why didn't the file open? */
   }
   return 0;
}

this program is copying the address of colour into image. Since the next sscanf() will overwrite the content of colour, all i ever will get is the last colour FOR ALL of my image[0..n] entries. how can i fix this problem

rectangle 0 0 1 1  orange
rectangle 0 1 1 1  green
rectangle 0 2 1 1  white
rectangle 0 3 1 1  orange
rectangle 0 4 1 1  white
rectangle 0 5 1 1  black
rectangle 0 6 1 1  blue
rectangle 0 7 1 1  red
rectangle 0 8 1 1  blue
rectangle 0 9 1 1  white
rectangle 0 10 1 1  green
rectangle 0 11 1 1  green
rectangle 0 12 1 1  orange
rectangle 0 13 1 1  red
rectangle 0 14 1 1  white
rectangle 0 15 1 1  green
rectangle 0 16 1 1  red
rectangle 0 17 1 1  black

input1.txt file include 1000 line something like that

You've already pinpointed the problem. You're storing the address of your input buffer rather than making a copy of the input string. As such, all references to the color will reflect the current contents of the buffer. If you don't want that, you'll have to make a copy each time.

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