CODEWITHSUNDEEP
c
Manny
Manny

Reputation: 669

converting a integer to a string

I have used rand function to generate a random number. I want to collect this number to a char buffer[10] or to a char *ptr

main()
{
    char *ptr;
    int a;
    srand(time(NULL));
    a = rand();
}

I want to copy the value in a to a buffer or point it by char *ptr, please help me out in this

Upvotes: 0

Views: 262

Answers (5)

Steve Jessop
Steve Jessop

Reputation: 279215

Just for reference, here's how to use snprintf when you don't know in advance how big the buffer needs to be:

size_t len = snprintf(NULL, 0, "%d", a) + 1;
char *ptr = malloc(len);
if (!ptr) {
    // memory allocation failed, you must decide how to handle the error
} else {
    snprintf(ptr, len, "%d", a);

    ... // some time later

    free(ptr);
}

However, since your code is written in an old style (no return type for main and all variables declared at the start of the function), it may be that your C implementation doesn't have snprintf. Beware that Microsoft's _snprintf is not a direct substitute: when it truncates the output it doesn't tell you how much data there is to write.

In this case you can use the value RAND_MAX to work out how many digits the value might have, and hence how big your buffer needs to be. 10 is not sufficient on Linux, where RAND_MAX is 2147483647, and so you need 11 bytes for your nul-terminated string.

Btw, I've neglected the possibility of snprintf indicating an error other than truncation, which it does with the return value -1. That's because %d can't fail.

Upvotes: 3

MOHAMED
MOHAMED

Reputation: 43518

char ptr[10];
sprintf(ptr,"%d",a);

If you want to use char *ptr

char *ptr = malloc(10*sizeof(char));
sprintf(ptr,"%d",a);

// And If you want to free allocated space for ptr some where:
free(ptr);

Upvotes: 0

jacekmigacz
jacekmigacz

Reputation: 789

If your compiler is GCC:

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

main()
{
    char *ptr;
    int a;
    srand(time(NULL));
    a = rand();
    asprintf(&ptr, "%d", a);
    printf("%s\n", ptr);
    //DO SOMETHING
    free(ptr);
}

Upvotes: 0

user529758
user529758

Reputation:

It's safer to use snprintf().

int answer = 42;
char buf[32];
snprintf(buf, sizeof(buf), "%d", answer);
printf("The answer is: %s\n", buf);

If you want to use a dynamically allocated buffer:

const size_t size = 32;
char *buf = malloc(size);
if (buf != NULL) {
    snprintf(buf, size, "%d", answer);
}

Upvotes: 0

Florin Petriuc
Florin Petriuc

Reputation: 1176

You can use 

char x[10];
sprintf(x, "%d", integer_number);

Upvotes: 1

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