How do I print center aligned string in C [duplicate]

问题

Can anyone help me in printing the string aligned to center in C?

For example:

int main()
{
    int a = 20;
    char x[10] = "Hello";
    char y[10] = "Hello";
    printf ("%*s\n",a, x );
    printf ("%-*s\n",a,y);
}

In the above the first prints Hello aligned to the right and the second printf to the left like this

                    Hello
Hello

restricting the length for each to 20.

Is there a way to print Hello aligned to the center.

        Hello

restricting the total length to 20.

Thankyou in advance

回答1:

In general, you probably want to avoid centre-aligned text, especially on a console, but in any case; this will take some doing.

The (likely) reason that printf doesn't know how to do this to begin with is that it's not an entirely deterministic operation; not all strings can be centred in all spaces.

Notably, unless space_for_string - strlen(string) is an even number, you're going to have to make a choice regarding where you want the string to be shifted to.

In any case, you do want to use the "%*s"specifier, but the number you feed into the width field can't be as simple as a flat 20.

Instead you want to feed it half the width of your space plus half the width of your string.

int main()
{
  int space = 20;
  char *string = "Hello";
  printf ("%*s\n", space / 2 + strlen(string) / 2,string);
}

回答2:

There is no standardised way to do this with the C stdio library. You would have to write your own code to do it with *printf calls or with your own printf format specifier.

This is a fast and dirty way to do it:

int main()
{
    int a = 20;
    char x[] = "Hello";

    int length = strlen(x);

    printf ("%*s%*c"
            ,((a - length) >> 1) + length // string length + padding spaces
            , x
            , ((a - length) >> 1) + ((a - length) & 1) // tailing spaces
            , ' '
    );
}

回答3:

You can use ncurses library to get to center of a line in terminal and printing your text if you are working on linux.

回答4:

You could, as Williham Totland's answer shows just calculate the required spaces, and use printf. Since I'm in the process of refreshing my knowledge (limited though it is), on memory management, I came up with this:

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

int main()
{
    int a = 20;
    char x[10] = "Hello";
    char *spaces_ptr;//padding str pointer
    a = (a-strlen(x))/2;
    //allocate the required mem, calloc ensures zero terminated
    spaces_ptr = calloc(a + 1, sizeof(char));
    memset(spaces_ptr, ' ', a);//set a chars to hold spaces
    //print
    printf("%s%s", spaces, x);
    free(spaces);//free memory
    return 0;
}

Using sprintf or strncat is an option, too, of course... or even:

char *fullStr = calloc(strlen(x) + a + 1, sizeof(char));
memset(fullStr, ' ', a);
strncpy(fullStr+a, x, strlen(x));
puts(fullStr);
free(fullStr);

Note that this last snippet is an afterthought, as is the entire answer, really... anyway check this codepad to see it in action

回答5:

Take a look at my tiny library: libTprint, the code is very simple and you should be able to understand how does it align texts.

Hope it helps you !

来源：https://stackoverflow.com/questions/19492858/how-do-i-print-center-aligned-string-in-c

标签

printf

centering

stdio