format string with variable in c

Question

I am writing in c. I want to make a character moving on screen while running time .I am thinking about using printf() which can print the screen after a specified number of white spaces using %s.

I am saving this number in a variable how can I use %s with variable not constant value

The code is

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

int main()
{
  int it=0;
  int tr;
  printf("T \n");
  srand(time(NULL));
  while(it != 80 )
  {
   tr=rand()%3+1;
   switch(tr)
   {
       int tmove=it;
       case 1 :{
           if(80-it>1)
           {
               tmove+=1;
               it+=1;
           }
           else it=80;
          break;}
       case 2 :{
           if(80-it>2)
            {
                tmove=+2;
                it+=2;
            }
           else it=80;
          break;}
       case 3 :{
           if(80-it>3)
           {
               tmove+=3;
               it+=3;
           }
           else it=80;
          break;}
            default:break;
   }
   printf("%s","T");
 }
 }

I want to make T printed after number of whitecaps equal to move.

Any chance you can rephrase your question in a less-obfuscated manner? — barak manos
– barak manos, Commented Dec 20, 2014 at 13:57
I extended my answer since I noticed some improvements that can be made. — Iharob Al Asimi
– Iharob Al Asimi, Commented Dec 20, 2014 at 20:39

Iharob Al Asimi · Accepted Answer · 2014-12-20 20:36:12Z

Use the length format specifier

printf("%*s%s\n", tmove, " ", "T");

Also, notice that each switch case can be written this way

if (80 - it > tr)
{
    tmove += tr;
    it    += tr;
}
else
    it = 80;

Hence you don't really need the switch you can just write

tr = rand() % 3 + 1;
if (80 - it > tr)
{
    tmove += tr;
    it    += tr;
}
else if (it > 3) /* for the default case of the switch */
    it = 80;

So the whole program transforms to

int main()
{
    int it = 0;
    int tr;

    printf("T\n");

    srand(time(NULL));
    while (it != 80 )
    {
        int tmove = it;
        tr = rand() % 3 + 1;
        if ((80 - it) > tr)
        {
            tmove += tr;
            it    += tr;
        }
        else if (it > 3)
            it = 80;
        printf("%*s%s", tmove, " ", "T");
    }
    return 0;
}

And judging for the first printf in your code, and the fact that tmove is always increasing I would say that you also need a newline character in the second printf, the ouput looks interesting, what is it?

int main()
{
    int it = 0;
    int tr;

    printf("T\n");

    srand(time(NULL));
    while (it != 80 )
    {
        int tmove = it;
        tr = rand() % 3 + 1;
        if ((80 - it) > tr)
        {
            tmove += tr;
            it    += tr;
        }
        else if (it > 3)
            it = 80;
        printf("%*s%s\n", tmove, " ", "T");
    }
    return 0;
}

one more tip, make the 3 a variable so you can modify it when you need to wihout having to change it everywhere

int main()
{
    int it = 0;
    int tr;
    int maximum = 3;

    printf("T\n");

    srand(time(NULL));
    while (it != 80 )
    {
        int tmove = it;
        tr = rand() % maximum + 1;
        if ((80 - it) > tr)
        {
            tmove += tr;
            it    += tr;
        }
        else if (it > maximum)
            it = 80;
        printf("%*s%s\n", tmove, " ", "T");
    }
    return 0;
}

this was one ouput for maximum = 3

Note: code never executes tmove=it, so tmove does not have a predictable value (Think of switch/case as a goto). Also tmove is out of scope if printf("%*s%s\n", tmove, " ", "T"); is to replace printf("%s","T");.
thanx a lot. i am trying trying to make T moves on screen while running ,i am thinking about clearing console each time in while loop -_- but it doesn't work

user12448 · Accepted Answer · 2014-12-20 14:15:59Z

0

you can use the function clrscr() by adding #include <conio.h> and create a variable nb for making left shift after that you can print the name, in the variable name for instance,

printf("%*s",nb,name);

you can put all that in a loop and each time clear the screen, increment the nb variable and finally print the name you can see it moving

for those who are using linux

to use the clear screen you need to add #include <stdlib.h> and make system("clear screen")

edited Dec 20, 2014 at 14:15

answered Dec 20, 2014 at 14:05

user12448

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1 Comment

user12448 Over a year ago

Thanks for mentioning that ! :)

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