Simple game - problem with array (I suppose)

There's so much here, it's hard to know where to start, but lets begin here:

int pos_rand(char *array)
{
    srand(time(NULL));    
    return (rand() % 10) * 2 + 1;   // recieve an odd random number between 1 to 21.
}

First off, there doesn't seem to be any point to the argument char *array as array is not used anywhere in the array.
Secondly, srand() is only used to seed the random number generator, and would normally only be used once per program. Consider the following program:

#include <stdlib.h>
#include <time.h>

int getrand()
{
    srand(time(NULL));
    return rand();
}


int main()
{
    for(int i = 0; i < 10; ++i)
        printf("%d\n", getrand());

    return 0;
}

The output for this program might look like this:

$ ./example
1824823912
1824823912
1824823912
1824823912
1824823912
1824823912
1824823912
1824823912
1824823912
$

What's happening here is that rand() gets its starting point reset every time, so as long as the call to getrand() is within the same second on the clock, it will return the same value.

Then there's this usage: *(array + i). Unless you're working on an obfuscated C program, that's not how you would typically access the i'th element of an array. The normal way to do it is array[i]

Next make sure you've compiled your program with -g option (adds in info for debugger) e.g. gcc -Wall -Wextra -g myprog.c -o myprog
Then use gdb to take examine what's going on
You may want to look at the gdb documentation and find out how to run a program, get the backtrace, change frames and print the values of variables.

Not the question, but ...
This code retruns an odd random number between 1 to 19.

return (rand() % 10) * 2 + 1;   // recieve an odd random number between 1 to 21.

change to

return (rand() % 11) * 2 + 1;

to get desired result.

return (rand() % 10) * 2 + 1;   // return an odd random number in [1,19]

I will just address the random number issue. Firstly, there are (at least) two ways to seed the random number generator (RNG). Pseudo-randomly or with a fixed number. For game purposes, it is often useful to use a fixed number so you can come back and use the same sequence of random values. You can call this the game number as is often done in card games. The pseudo-random way is to use the time. If you use srand and rand, the random values will range from 0 to RAND_MAX which is usually 32,767. Here is a little function that will seed the RNG for you :

typedef unsigned short USHORT;

#define PSEUDO_RANDOM_SEED 0

void SeedRNG( USHORT seedVal )
{
    USHORT seed = seedVal;
    if( seedVal == PSEUDO_RANDOM_SEED )
    {
        time_t now = time( NULL );
        seed = (USHORT)( now % RAND_MAX );
    }
    srand( seed );
}

That will allow you to see the RNG either way - pseudo-randomly by passing 0 or in a repeated way by passing a non-zero value.

It is important to seed the RNG only one time.

Here is a handy random number generation function. You can specify the range of values you want to span.

int GetRandomInt( int minval, int maxval )
{
    int range = maxval - minval + 1;
    int value = rand() % range;   // limit the value to the range of interest
    return range + minval;        // offset it by minimum to get it into the ROI
}

Lastly, here is how you can use them.

void Testem()
{
    const int valueCount = 20;
    int value;

    SeedRNG( PSEUDO_RANDOM_SEED );

    for( int n = 0; n < valueCount; ++n )
    {
        value = GetRandomInt( 10, 90 );
        printf( "value %2d is %2d\n", n + 1, value );
    }
}

This little sample should print twenty random values ranging between 10 to 90.

Thank you all guys.I used malloc and free and it worked.
Now I want to "blink" the star "*" between "|" ,but I want to generate odd random numbers without being repeated in successive positions:
For example ,I use a for loop,so:
If i = 1 ,then I generate an odd random number in [1 , 19].
When i = 2 ,I want to generate an odd random number between [1 , 19],except previous number(i = 1).
When i = 3, I 'm able to use the number of (loop: i = 1) ,but not number in
(loop: i = 2) ,etc...


I thought and tried something but doesnn't work good and it sticks.
Whole code:

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


int pos_rand(char *array);
void delay(int number_of_seconds);
void run(char *array);
int change_pos(char *array , int ps);


int main(void)
{
    char *array;
    for(int i = 1; i <= 10; i++)
    {
        run(array);
        system("clear");
    }
    
}


int pos_rand(char *array)
{
    srand(time(NULL));    
    return (rand() % 10) * 2 + 1;   // recieve an odd random number between 1 to 19.
}




void delay(int number_of_seconds) 
{ 
    // Converting time into milli_seconds 
    int milli_seconds = 1000 * number_of_seconds; 
  
    // Storing start time 
    clock_t start_time = clock(); 
  
    // looping till required time is not achieved 
    while (clock() < start_time + milli_seconds); 
} 


void run(char *array)
{
    printf("Array:");
    for (int i = 0; i <= 7; i++)
    {
        printf(" ");
    }

    array = malloc(sizeof(char) * 21);
    if(!array)
    {
        printf("ERROR\n");
        exit(0);
    }

    for(int i = 0; i <= 9; i++)
    {
        array[ change_pos(array , i) ] = '*';
    }
    
    
    
    for (int i = 0; i <= 20; i++)
    {

        if(i % 2 == 0 && array[i] != '*')
        {
            array[i] = '|';
        }
        
        else if(array[i] != '*')
        {
            array[i] = ' ';
        }
    }
    
    for (int i = 0; i <= 20; i++)
    {
        printf("%c" , array[i]);
    }
    
    printf("\n\nPosition:      ");

    for (int i = 1; i <= 10; i++)
    {
        printf("%d " , i);
    }
    delay(300);
    printf("\n");
    for (int i = 0; i <= 20; i++)
    {
        array[i] = ' ';
    }

    printf("\n");
    free(array);
}



int change_pos(char *array , int ps)
{
    int *arr_pos;
    int previous;
    
    arr_pos = malloc(sizeof(int) * 10);
    do
    {
        previous = pos_rand(array);
        arr_pos[ps] = previous;
    }
    while(arr_pos[previous] == arr_pos[previous + 1]);
    free(arr_pos);
    return previous;
}

To new question:

Quote:

Now I want to "blink" the star "*" between "|" ,but I want to generate odd random numbers without being repeated in successive positions:

Random numbers without repeat are not random!
Think of a deck of cards, you shuffle all the deck at once, then you draw cards 1 by 1. when all cards draw, shuffle again.
Shuffling - Wikipedia[^]
Fisher–Yates shuffle - Wikipedia[^]